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CPCS 203 Lab sheet 4Student Name: _____________________________ Section: __

King Abdulaziz UniversityFaculty of Computing and Information Systems

Spring Term 2012/1433

Course Code: CPCS-203 Course Name:

Programming II _________________________________________________________________ _____

Objectives

In this chapter you will learn:

The concept of polymorphism.

To use overridden methods to effect polymorphism.

To distinguish between abstract and concrete classes.

To declare abstract methods to create abstract classes. How polymorphism makes systems extensible and maintainable.

To determine an object’s type at execution time.

To declare and implement interfaces.

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Prelab Activity:

Matching

The questions are intended to test and reinforce your understanding of key concepts. You may answerthe questions before the lab.

For each term in the left column, write the letter for the description from the right column that bestmatches the term.

Term Description

I 1. abstract method a) Can be used in place of an abstract class when thereis no default implementation to inherit.

J 2. getClass method b) Indicates that a method cannot be overridden orthat a class cannot be a su per class.

H 3 . implements keyword c) Class method which returns the name of the classassociated with the Class object.

L 4 . type-wrapper classes d) An operator that returns true if its left operand (avariable of a reference type) has the is-a relationshipwith its right operand (a class or interface name).

F 5 . downcasting e) Uses superclass references to manipulate sets ofsubclass objects in a generic manner.

K 6 . concrete class f) Casting a superclass reference to a subclassreference.

E 7 . polymorphism g) Cannot be instantiated; used primarily forinheritance.

D 8 . instanceof h) Indicates that a class will declare each method inan interface with the signature specified in theinterface declaration.

B 9 . final i) Must be overridden in a subclass; otherwise, the

subclass must be declared abstract.

C 10. getName method j) Returns an object that can be used to determineinformation about the object’s class.

G 11. abstract class k) A class that can be used to create objects.

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A 12. interface l) Classes in the java.lang package that are used tocreate objects containing values of primitive types.

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Prelab Activity:

Short Answers

10. Describe the concept of polymorphism.

Polymorphism makes it possible to design and implement systems that are more easilyextensible. Programs can be written to process objects generically as one type, and newclasses can be added with little or no modifications to the generic part of the program. Forexample, a program can be designed to draw shapes rather than to draw rectangles, ovalsand lines. Each shape object would know how to draw itself.

11. Define what it means to declare a method final and what it means to declare a classfinal.

Declaring a method final means that the method cannot be overridden in a subclass.Declaring a class final means that it cannot be a superclass (i.e., a class cannot inherit froma final class). Methods in a final class are implicitly final.

12. What happens when a class specifies that it implements an interface, but does not provide declarations of all the methods in the interface?

A compilation error occurs in this case. Every method in the interface must beimplemented, or the class must be declared abstract to prevent this compilation error.

13. Describe how to determine the class name of an object’s class.

Call method getClass on an object to obtain an object of type Class that represents the

object’s type. Then call the Class object’s getName method to get a String containing theclass’s name.

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14. Distinguish between an abstract class and a concrete class.

An abstract class can be used as a superclass and to declare variables that can storereferences to objects of the abstract class’s subclass. An abstract class cannot be used to

create objects. A concrete class can be used to create objects and declare variables. Inaddition, a concrete class can also be used as a superclass as long as it is not declared final.

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42 // set social security number 43 public void setSocialSecurityNumber( String ssn ) 44 { 45 socialSecurityNumber = ssn; // should validate 46 } // end method setSocialSecurityNumber 47

48 // return social security number 49 public String getSocialSecurityNumber() 50 { 51 return socialSecurityNumber; 52 } // end method getSocialSecurityNumber 53

54 // return String representation of Employee object 55 public String toString() 56 { 57 return String.format( "%s %s\nsocial security number: %s", 58 getFirstName(), getLastName(), getSocialSecurityNumber() ); 59 } // end method toString 60

61 // abstract method overridden by subclasses

62 public abstract double earnings(); // no implementation here 63 } // end abstract class Employee

Fig. 1 | Employee abstr act superclass. (Part 2 of 2)

1 // SalariedEmployee.java 2 // SalariedEmployee class extends Employee. 3

4 public class SalariedEmployeeextends Employee 5 { 6 private double weeklySalary; 7

8 // f our-argument constructor 9 public SalariedEmployee( String first, String last, String ssn,

10 double salary ) 11 { 12 super( first, last, ssn ); // pass to Employee constructor 13 setWeeklySalary( salary ); // validate and store salary 14 } // end four-argument SalariedEmployee constructor 15

16 // set salary 17 public void setWeeklySalary( double salary ) 18 { 19 weeklySalary = salary < 0.0 ? 0.0 : salary; 20 } // end method setWeeklySalary

21

22 // return salary 23 public double getWeeklySalary()

24 { 25 return weeklySalary; 26 } // end method getWeeklySalary 27

28 // calculate earnings; override abstract method earnings in Employee 29 public double earnings() 30 {

31 return getWeeklySalary(); 32 } // end method earnings 33

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34 // return String representation of SalariedEmployee object 35 public String toString() 36 { 37 return String.format( "salaried employee: %s\n%s: $%,.2f", 38 super.toString(), "weekly salary", getWeeklySalary() ); 39 } // end method toString 40 } // end class SalariedEmployee

Fig. 2 | SalariedEmployee class derived from Employee.

1 // CommissionEmployee.java 2 // CommissionEmployee class extends Employee. 3

4 public class CommissionEmployee extends Employee 5 { 6 private double grossSales; // gross weekly sales 7 private double commissionRate; // commission percentage 8

9 // f ive-argument constructor 10 public CommissionEmployee( String first, String last, String ssn, 11 double sales, double rate ) 12 { 13 super( first, last, ssn ); 14 setGrossSales( sales ); 15 setCommissionRate( rate ); 16 } // end five-argument CommissionEmployee constructor 17

18 // set commission rate 19 public void setCommissionRate( double rate ) 20 { 21 commissionRate = ( rate > 0.0 && rate < 1.0 ) ? rate : 0.0; 22 } // end method setCommissionRate 23

24 // return commission rate

25 public double getCommissionRate() 26 { 27 return commissionRate; 28 } // end method getCommissionRate 29

30 // set gross sales amount 31 public void setGrossSales( double sales ) 32 { 33 grossSales = ( sales < 0.0 ) ? 0.0 : sales; 34 } // end method setGrossSales 35

36 // return gross sales amount 37 public double getGrossSales() 38 { 39 return grossSales; 40 } // end method getGrossSales 41

42 // calculate earnings; override abstract method earnings in Employee 43 public double earnings() 44 { 45 return getCommissionRate() * getGrossSales(); 46 } // end method earnings 47

48 // return String representation of CommissionEmployee object

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49 public String toString() 50 { 51 return String.format( "%s: %s\n%s: $%,.2f; %s: %.2f", 52 "commission employee", super.toString(), 53 "gross sales", getGrossSales(), 54 "commission rate", getCommissionRate() ); 55 } // end method toString

56 } // end class CommissionEmployee

Fig. 3 | CommissionEmployee class derived from Employee.

15. What is output by the following code segment? Assume that the code appears in the main method of an

application.

1 SalariedEmployee employee1 = 2 new SalariedEmployee( "June", "Bug", "123-45-6789", 1000.00 ); 3

4 CommissionEmployee employee2 = 5 new CommissionEmployee( "Archie", "Tic", "987-65-4321", 15000.00, 0.10 ); 6

7 System.out.printf( "Employee 1:\n%s\n\n", employee1 ); 8 System.out.printf( "Employee 2:\n%s\n\n", employee2 );

Your an swer :

Employee 1: salaried employee: June Bug social security number: 123-45-6789 weekly salary: $1,000.00

Employee 2: commission employee: Archie Tic social security number: 987-65-4321 gross sales: $15,000.00; commission rate: 0.10

16. What is output by the following code segment? Assume that the code appears in the main method of an

application.

1 Employee firstEmployee = 2 new SalariedEmployee( "June", "Bug", "123-45-6789", 1000.00 ); 3

4 Employee secondEmployee = 5 new CommissionEmployee( "Archie", "Tic", "987-65-4321", 15000.00, 0.10 );

6

7 System.out.printf( "Employee 1:\n%s\n\n", firstEmployee ); 8 System.out.printf( "Employee 2:\n%s\n\n", secondEmployee );

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Your an swer :

Employee 1: salaried employee: June Bug social security number: 123-45-6789 weekly salary: $1,000.00

Employee 2: commission employee: Archie Tic social security number: 987-65-4321 gross sales: $15,000.00; commission rate: 0.10

17. What is output by the following code segment? Assume that the code follows the statements in Pr o g rammin g

Output Exer ci se 28.

1 SalariedEmployee salaried = ( SalariedEmployee ) firstEmployee;

2 System.out.printf( "salaried:\n%s\n", salaried );

Your an swer :

salaried: salaried employee: June Bug social security number: 123-45-6789 weekly salary: $1,000.00

18. What is output by the following code segment? Assume that the code follows the statements in Pr o g rammin g

Output Exer ci se 17 .

1 CommissionEmployee commission = ( CommissionEmployee ) firstEmployee; 2 System.out.println( "commission:\n%s\n", commission );

Your an swer :

Although the cast in line 1 is allowed at compile time, this results in a ClassCastException at run- time because a SalariedEmployee is not a CommissionEmployee.

Exception in thread "main" java.lang.ClassCastException:

SalariedEmployee at Test.main(Test.java:17)

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Prelab Activity:

Correct the Code

Determine if there is an error in each of the following program segments. If there is an error,specify whether it is a logic error or a compilation error, circle the error in the program andwrite the corrected code in the s pace provided after each problem. If the code does notcontain an error, write ―no er ror.‖ [ Not e: There may be more than one error in each programsegment.]

For que stions 19 – 33 assume the following d e finit ion of abstract class

Employee.

1 // Employee abstract superclass. 2

3 public abstract class Employee 4 { 5 private String firstName; 6 private String lastName; 7

8 // three-argument constructor 9 public Employee( String first, String last )

10 { 11 f irstName = first; 12 lastName = last; 13 } // end three-argument Employee constructor 14

15 // return first name 16 public String getFirstName() 17 {

18 return firstName; 19 } // end method getFirstName 20

21 // return last name 22 public String getLastName() 23 { 24 return lastName; 25 } // end method getLastName 26

27 // return String representation of Employee object 28 public String toString() 29 { 30 return String.format( "%s %s", getFirstName(), getLastName() ); 31 } // end method toString 32

33 // abstract method overridden by subclasses 34 public abstract double earnings(); // no implementation here 35 } // end abstract class Employee

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19. The following concrete class should inherit from abstract class Employee. A TipWorker is paid by the

hour plus their tips for the week.

1 // TipWorker.java 2 public final class TipWorker extends Employee 3 {

4 private double wage; // wage per hour 5 private double hours; // hours worked f or week 6 private double tips; // tips f or the week 7

8 public TipWorker( String first, String last, 9 double wagePerHour, double hoursWorked, double tipsEarned )

10 { 11 super( first, last ); // call superclass constructor 12 setWage ( wagePerHour ); 13 setHours( hoursWorked ); 14 setTips( tipsEarned ); 15 } 16

17 // set the wage

18 public void setWage( double wagePerHour ) 19 { 20 wage = ( wagePerHour < 0 ? 0 : wagePerHour ); 21 } 22

23 // set the hours worked 24 public void setHours( double hoursWorked ) 25 { 26 hours = ( hoursWorked >= 0 && hoursWorked < 168 ? hoursWorked : 0 ); 27 } 28

29 // set the tips 30 public void setTips( double tipsEarned ) 31 { 32 tips = ( tipsEarned < 0 ? 0 : tipsEarned );

33 } 34 } // end class TipWorker

Your an swer :

Class TipWorker did not implement abstract method earnings that was inherited from class Employee. The class must implement this method to be a concrete class.

1 // TipWorker.java 2 public final class TipWorker extends Employee 3 { 4 private double wage; // wage per hour

5 private double hours; // hours worked f or week 6 private double tips; // tips f or the week 7

8 public TipWorker( String first, String last, 9 double wagePerHour, double hoursWorked, double tipsEarned )

10 { 11 super( first, last ); // call superclass constructor 12 setWage ( wagePerHour ); 13 setHours( hoursWorked ); 14 setTips( tipsEarned ); 15 }

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21. The following code should input information about five TipWorkers from the user and then print that

information and all the TipWorkers’ calculated earnings.

1 // Test2.java 2 import java.util.Scanner; 3

4 public class Test2 5 { 6 public static void main( String args[] ) 7 { 8 Employee employee[]; 9 Scanner input = new Scanner( System.in );

10

11 for ( int i = 0; i < employee.length; i++ ) 12 { 13 System.out.print( "Input first name: " ); 14 String firstName = input.nextLine(); 15

16 System.out.print( "Input last name: " ); 17 String lastName = input.nextLine();

18 19 System.out.print( "Input hours worked: " ); 20 double hours = input.nextDouble(); 21

22 System.out.print( "Input tips earned: " ); 23 double tips = input.nextDouble(); 24

25 employee[ i ] = new Employee( firstName, lastName, 2.63, hours, tips ); 26

27 System.out.printf( "%s %s earned $%.2f\n", employee[ i ].getFirstName(), 28 employee[ i ].getLastName(), employee[ i ].earnings() ); 29

30 input.nextLine(); // clear any remaining characters in the input stream 31 } // end f or 32 } // end main 33 } // end class Test2

Your an swer :

1 // Test2.java 2 import java.util.Scanner; 3

4 public class Test2 5 { 6 public static void main( String args[] ) 7 { 8 Employee employee[] = new Employee[ 5 ];

9 Scanner input=

new Scanner( System.in ); 10

11 for ( int i = 0; i < employee.length; i++ ) 12 { 13 System.out.print( "\nInput first name: " ); 14 String firstName = input.nextLine(); 15

16 System.out.print( "Input last name: " ); 17 String lastName = input.nextLine();

18

19 System.out.print( "Input hours worked: " );

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20 double hours = input.nextDouble(); 21

22 System.out.print( "Input tips earned: " ); 23 double tips = input.nextDouble(); 24

25 employee[ i ] = new TipWorker( firstName, lastName, 2.63, hours, tips ); 26

27 System.out.printf( "%s %s earned $%.2f\n", employee[ i ].getFirstName(), 28 employee[ i ].getLastName(), employee[ i ].earnings() ); 29

30 input.nextLine(); // clear any remaining characters in the input stream 31 } // end f or 32 } // end main 33 } // end class Test2

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Lab Exercises:

Lab Exercise 1 — Payroll System Modification

This problem is intended to be solved in a closed-lab session with a teaching assistant or instructor present. The

problem is divided into six par ts:

1. Lab O b jectives

2. Description of the Problem

3. Sample Out put

4. Program Template (Fig. L 4 – Fig. 5)

5. Problem-Solving Tips

6. Follow-Up Question and Activity

The program template represents a complete working Java program, with one or more key lines of code replacedwith comments. Read the problem description and examine the sample output; then study the template code.Using the problem-solving t ips as a guide, replace the /* */ comments with Java code. Compile and execute the

program. Compare your output with the sample output provided. Then answer the follow-up questions. Thesource code for the template is available at www.pearsonhighered.com/deitel.

Lab Objectives

This lab was designed to reinforce programming concepts from Chapter 10 of Java How to Program: 8/e. In this lab, you will practice:

Creating a new class and adding it to an existing class hierarchy.

Using the updated class hierarchy in a polymorphic application.

The follow-up question and activity also will give you practice:

Understanding polymorphism.

Descr iption of the Problem

(Payroll System Modification) Modify the payroll system of Figs. 4 – 9 to include an additional Employee subclass

PieceWorker that represents an employee whose pay is based on the number of pieces of merchandise produced.

Class PieceWorker should contain private instance variables wage (to store the employee’s wage per piece) andpieces (to store the number of pieces produced). Provide a concrete implementation of method earnings in class

PieceWorker that calculates the em ployee’s earnings by multiplying the number of pieces produced by the wage

per piece. Create an array of Employee variables to store references to objects of each concrete class in the newEmployee hierarchy. For each Employee, display its string representation and earnings.

http://www.pearsonhighered.com/deitel









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CPCS 203 Lab sheet 4Student Name: _____________________________ Section: __25 // return pieces produced

26 /* write a get method that returns the number of pieces produced */ 27

28 // calculate earnings; override abstract method earnings in Employee 29 public double earnings() 30 { 31 /* write code to return the earnings for a PieceWorker */

32 } // end method earnings 33

34 // return String representation of PieceWorker object 35 public String toString() 36 { 37 /* write code to return a string representation of a PieceWorker */

38 } // end method toString 39 } // end class PieceWorker

Fig. 4 | PieceWorker.java. (Par t 2 of 2.)

1 // Lab Exercise 1: PayrollSystemTest.java 2 // Employee hierarchy test program. 3

4 public class PayrollSystemTest 5 { 6 public static void main( String args[] ) 7 { 8 // create five-element Employee array 9 Employee employees[] = new Employee[ 5 ]; 10

11 // initialize array with Employees 12 employees[ 0 ] = new SalariedEmployee( 13 "John", "Smith", "111-11-1111", 800.00 ); 14 employees[ 1 ] = new HourlyEmployee( 15 "Karen", "Price", "222-22-2222", 16.75, 40 ); 16 employees[ 2 ] = new CommissionEmployee( 17 "Sue", "Jones", "333-33-3333", 10000, .06 ); 18 employees[ 3 ] = new BasePlusCommissionEmployee( 19 "Bob", "Lewis", "444-44-4444", 5000, .04, 300 );

20 /* create a PieceWoker object and assign it to employees[ 4 ] */ 21

22 System.out.println( "Employees processed polymorphically:\n" ); 23

24 // generically process each element in array employees 25 for ( Employee currentEmployee : employees ) 26 { 27 System.out.println( currentEmployee ); // invokes toString 28 System.out.printf( 29 "earned $%,.2f\n\n", currentEmployee.earnings() ); 30 } // end f or 31 } // end main 32 } // end class PayrollSystemTest

Fig. 5 | PayrollSystemTest. java

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Solution

1 // Lab Exercise 1: PieceWorker 2 // PieceWorker class extends Employee. 3

4 public class PieceWorker extends Employee 5 { 6 private double wage; // wage per piece

7 private int pieces; // pieces of merchandise produced in week 8

9 // f ive-argument constructor 10 public PieceWorker( String first, String last, String ssn, 11 double wagePerPiece, int piecesProduced ) 12 { 13 super( first, last, ssn ); 14 setWage( wagePerPiece ); // validate and store wage per piece 15 setPieces( piecesProduced ); // validate and store pieces produced 16 } // end five-argument PieceWorker constructor 17

18 // set wage 19 public void setWage( double wagePerPiece ) 20 { 21 wage = ( wagePerPiece < 0.0 ) ? 0.0 : wagePerPiece;

22 } // end method setWage 23

24 // return wage 25 public double getWage() 26 { 27 return wage; 28 } // end method getWage 29

30 // set pieces produced 31 public void setPieces( int piecesProduced ) 32 { 33 pieces = ( piecesProduced < 0 ) ? 0 : piecesProduced; 34 } // end method setPieces 35

36 // return pieces produced 37 public int getPieces() 38 { 39 return pieces; 40 } // end method getPieces 41

42 // calculate earnings; override abstract method earnings in Employee 43 public double earnings() 44 { 45 return getPieces() * getWage(); 46 } // end method earnings 47

48 // return String representation of PieceWorker object 49 public String toString() 50 {

51 return String.format( "%s: %s\n%s: $%,.2f; %s: %d", 52 "piece worker", super.toString(), 53 "wage per piece", getWage(), "pieces produced", getPieces() ); 54 } // end method toString 55 } // end class PieceWorker

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CPCS 203 Lab sheet 4Student Name: _____________________________ Section: __1 // Lab Exercise 1: PayrollSystemTest.java 2 // Employee hierarchy test program. 3

4 public class PayrollSystemTest 5 { 6 public static void main( String args[] ) 7 { 8 // create five-element Employee array 9 Employee employees[] = new Employee[ 5 ];

10 11 // initialize array with Employees 12 employees[ 0 ] = new SalariedEmployee( 13 "John", "Smith", "111-11-1111", 800.00 ); 14 employees[ 1 ] = new HourlyEmployee( 15 "Karen", "Price", "222-22-2222", 16.75, 40 ); 16 employees[ 2 ] = new CommissionEmployee( 17 "Sue", "Jones", "333-33-3333", 10000, .06 ); 18 employees[ 3 ] = new BasePlusCommissionEmployee( 19 "Bob", "Lewis", "444-44-4444", 5000, .04, 300 ); 20 employees[ 4 ] = new PieceWorker( 21 "Rick", "Bridges", "555-55-5555", 2.25, 400 ); 22


25 // generically process each element in array employees 26 for ( Employee currentEmployee : employees ) 27 { 28 System.out.println( currentEmployee ); // invokes toString 29 System.out.printf( 30 "earned $%,.2f\n\n", currentEmployee.earnings() ); 31 } // end f or 32 } // end main 33 } // end class PayrollSystemTest

Problem-Solving Tips

1. The PieceWorker constructor should call the superclass Employee constructor to initialize the employee’s

name.

2. The number of pieces produced should be greater than or equal to 0. Place this logic in the set method for thepieces variable.

3. The wage should be greater than or equal to 0. Place this logic in the set method for the wage variable.

4. The main method must explicitly create a new PieceWorker object and assign it to an element of the

employees array.

5. If you have any questions as you proceed, ask your lab instructor for assistance.

Follow-Up Question and Activity

1. Explain the line of code in your PayrollSystemTest’s main method that calls method earnings. Why canthat line invoke method earnings on every element of the employees array?

This line of code uses polymorphism to ensure that each Employee’s earnings is calculated correctly. Everyelement of array employees refers to an object that is an Employee. Since class Employee declares an abstract

earnings method, every concrete subclass of Employee must implement the earnings method. Also, sinceobjects can be created only from concrete classes, it is guaranteed that the object to which currentEmployee

refers during an iteration of the for statement will have an earnings method.

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Lab Exercises:

Lab Exercise 2 — Accounts Paya ble System Modif ication

This problem is intended to be solved in a closed-lab session with a teaching assistant or instructor present. The problem is divided into six par ts:

1. Lab O b jectives

2. Description of the Problem

3. Sample Out put

4. Program Template (Fig. L 10.6 – Fig. L 10.9)

5. Problem-Solving Tips

6. Follow-Up Question and Activity

The program template represents a complete working Java program, with one or more key lines of code replacedwith comments. Read the problem description and examine the sample output; then study the template code.

Using the problem-solving tips as a guide, replace the/* */

comments with Java code. Compile and execute the program. Compare your output with the sample output provided. Then answer the follow-up question. The

source code for the template is available at www.pearsonhighered.com/deitel.

Lab Objectives

This lab was designed to reinforce programming concepts from Chapter 10 of Java How to Program: 8/e. In this lab you will pr actice:

Provide additional polymorphic processing capabilities to an inheritance hierarchy by implementing aninterface.

Using the instanceof operator to determine whether avariable refers to an object that has an is-a relationshipwith a particular class.

The follow-up question and activity will also give you practice: Comparing interfaces and abstract classes.

Descr iption of the Problem

(Accounts Payable System Modi f icat ion) In this e x e r c i s e , we modify the accounts payableapplication of Figs. 11 – 15 to include the complete functionality of the payroll application. The applicationshould still process two Invoice objects, but now should process one object of each of the four Employee

subclasses (Figs. 5 – 8). If the object currently being processed is a BasePlusCommissionEmployee, theapplication should increase the BasePlusCommissionEmployee’s base salary by 10%. Finally, the applicationshould output the payment amount for each object. Complete the following steps to create the new application:

a) Modify classes HourlyEmployee and CommissionEmployee to place them in the Payable hierarchy as sub-

classes of the version of Employee that implements Payable (Fig. 13). [ Hint : Change the name of method earnings

to getPaymentAmount in each subclass so that the class satisfies its inherited contract with interface Payable.]

b) Modify class BasePlusCommissionEmployee such that it extends the version of class CommissionEmployee

created in Part a.

c) Modify PayableInterfaceTest to polymorphically process two Invoices, one SalariedEmployee, oneHourlyEmployee, one CommissionEmployee and one BasePlusCommissionEmployee. First output a stringrepresentation of each Payable object. Next, if an object is a BasePlusCommissionEmployee, increase its base salary

by 10%. Finally, output the payment amount for each Payable object.










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9 // f ive-argument constructor 10 public HourlyEmployee( String first, String last, String ssn, 11 double hourlyWage, double hoursWorked ) 12 { 13 super( first, last, ssn ); 14 setWage( hourlyWage ); // validate and store hourly wage 15 setHours( hoursWorked ); // validate and store hours worked

16 } // end five-argument HourlyEmployee constructor 17

18 // set wage 19 public void setWage( double hourlyWage ) 20 { 21 wage = ( hourlyWage < 0.0 ) ? 0.0 : hourlyWage; 22 } // end method setWage 23

24 // return wage 25 public double getWage() 26 { 27 return wage; 28 } // end method getWage 29

30 // set hours worked 31 public void setHours( double hoursWorked ) 32 { 33 hours = ( ( hoursWorked >= 0.0 ) && ( hoursWorked <= 168.0 ) ) ? 34 hoursWorked : 0.0; 35 } // end method setHours 36

37 // return hours worked 38 public double getHours() 39 { 40 return hours; 41 } // end method getHours 42

43 // calculate earnings; implement interface Payable method not 44 // implemented by superclass Employee

45 /* write a method header to satisfy the Payable interface */ 46 { 47 if ( getHours() <= 40 ) // no overtime 48 return getWage() * getHours(); 49 else 50 return 40 * getWage() + ( getHours() - 40 ) * getWage() * 1.5; 51 } // end method getPaymentAmount 52

53 // return String representation of HourlyEmployee object 54 public String toString() 55 { 56 return String.format( "hourly employee: %s\n%s: $%,.2f ; %s: %,.2f", 57 super.toString(), "hourly wage", getWage(), 58 "hours worked", getHours() ); 59 } // end method toString 60 } // end class HourlyEmployee

Fig. 6 | HourlyEmployee.java. (Par t 2 of 2.)

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1 // Lab Exercise 2: CommissionEmployee.java 2 // CommissionEmployee class extends Employee, which implements Payable. 3


9 // f ive-argument constructor

10 public CommissionEmployee( String first, String last, String ssn, 11 double sales, double rate ) 12 { 13 super( first, last, ssn ); 14 setGrossSales( sales ); 15 setCommissionRate( rate ); 16 } // end five-argument CommissionEmployee constructor 17


24 // return commission rate 25 public double getCommissionRate() 26 { 27 return commissionRate; 28 } // end method getCommissionRate 29

30 // set gross sales amount 31 public void setGrossSales( double sales ) 32 { 33 grossSales = ( sales < 0.0 ) ? 0.0 : sales; 34 } // end method setGrossSales 35

36 // return gross sales amount 37 public double getGrossSales() 38 {

39 return grossSales; 40 } // end method getGrossSales 41

42 // calculate earnings; implement interface Payable method not 43 // implemented by superclass Employee

44 /* write a method header to satisfy the Payable interface */ 45 { 46 return getCommissionRate() * getGrossSales(); 47 } // end method getPaymentAmount 48

49 // return String representation of CommissionEmployee object 50 public String toString() 51 { 52 return String.format( "%s: %s\n%s: $%,.2f; %s: %.2f", 53 "commission employee", super.toString(), 54 "gross sales", getGrossSales(), 55 "commission rate", getCommissionRate() ); 56 } // end method toString 57 } // end class CommissionEmployee

Fig. 7 | CommissionEmployee.java.

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CPCS 203 Lab sheet 4Student Name: _____________________________ Section: __1 // Lab Exercise 2: BasePlusCommissionEmployee.java 2 // BasePlusCommissionEmployee class extends CommissionEmployee. 3

4 public class BasePlusCommissionEmployee extends CommissionEmployee 5 { 6 private double baseSalary; // base salary per week 7

8 // six-argument constructor 9 public BasePlusCommissionEmployee( String first, String last,

10 String ssn, double sales, double rate, double salary ) 11 { 12 super( first, last, ssn, sales, rate ); 13 setBaseSalary( salary ); // validate and store base salary 14 } // end six-argument BasePlusCommissionEmployee constructor 15

16 // set base salary 17 public void setBaseSalary( double salary ) 18 { 19 baseSalary = ( salary < 0.0 ) ? 0.0 : salary; // non-negative 20 } // end method setBaseSalary 21

22 // return base salary 23 public double getBaseSalary() 24 {

25 return baseSalary; 26 } // end method getBaseSalary 27

28 // calculate earnings; override CommissionEmployee implementation of 29 // interface Payable method

30 /* write a method header to satisfy the Payable interface */ 31 { 32 /* calculate and return the BasePlusCommissionEmployee's earnings */

33 } // end method getPaymentAmount 34

35 // return String representation of BasePlusCommissionEmployee object 36 public String toString() 37 { 38 return String.format( "%s %s; %s: $%,.2f",

39 "base-salaried", super.toString(), 40 "base salary", getBaseSalary() ); 41 } // end method toString 42 } // end class BasePlusCommissionEmployee

Fig. 8 | BasePlusCommissionEmployee.java.

1 // Lab Exercise 2: PayableInterfaceTest.java 2 // Tests interface Payable. 3

4 public class PayableInterfaceTest 5 { 6 public static void main( String args[] ) 7 { 8 // create six-element Payable array 9 Payable payableObjects[] = new Payable[ 6 ]; 10

Fig. 9 | PayableInterfaceTest.java. (Par t 1 of 2.)

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CPCS 203 Lab sheet 4Student Name: _____________________________ Section: __11 // populate array with objects that implement Payable 12 payableObjects[ 0 ] = new Invoice( "01234", "seat", 2, 375.00 ); 13 payableObjects[ 1 ] = new Invoice( "56789", "tire", 4, 79.95 ); 14 payableObjects[ 2 ] = 15 new SalariedEmployee( "John", "Smith", "111-11-1111", 800.00 ); 16 payableObjects[ 3 ] = 17 /* create an HourlyEmployee object */ 18 payableObjects[ 4 ] =

19 /* create a CommissionEmployee object */

20 payableObjects[ 5 ] = 21 /* create a BasePlusCommissionEmployee object */ 22

23 System.out.println( 24 "Invoices and Employees processed polymorphically:\n" ); 25

26 // generically process each element in array payableOb jects 27 for ( Payable currentPayable : payableObjects ) 28 { 29 // output currentPayable and its appropriate payment amount 30 System.out.printf( "%s \n", currentPayable.toString() ); 31

32 /* write code to determine whether currentPayable is a 33 BasePlusCommissionEmployee object */ 34 {

35

36 /* write code to give a raise */ /* write code to ouput results of the raise */

37 } // end if 38

39 System.out.printf( "%s: $%,.2f\n\n", 40 "payment due", currentPayable.getPaymentAmount() ); 41 } // end f or 42 } // end main 43 } // end class PayableInterfaceTest

Fig. 9 | PayableInterfaceTest.java. (Par t 2 of 2.)

Solution

1 // Lab Exercise 2: HourlyEmployee.java 2 // HourlyEmployee class extends Employee, which implements Payable. 3

4 public class HourlyEmployee extends Employee 5 { 6 private double wage; // wage per hour 7 private double hours; // hours worked f or week 8

9 // f ive-argument constructor 10 public HourlyEmployee( String first, String last, String ssn, 11 double hourlyWage, double hoursWorked ) 12 {

13 super( first, last, ssn ); 14 setWage( hourlyWage ); // validate and store hourly wage 15 setHours( hoursWorked ); // validate and store hours worked 16 } // end five-argument HourlyEmployee constructor 17

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CPCS 203 Lab sheet 4Student Name: _____________________________ Section: __18 // set wage 19 public void setWage( double hourlyWage ) 20 { 21 wage = ( hourlyWage < 0.0 ) ? 0.0 : hourlyWage; 22 } // end method setWage 23

24 // return wage 25 public double getWage() 26 {

27 return wage; 28 } // end method getWage 29


37 // return hours worked 38 public double getHours() 39 { 40 return hours; 41 } // end method getHours

42

43 // calculate earnings; implement interface Payable method not 44 // implemented by superclass Employee 45 public double getPaymentAmount() 46 { 47 if ( getHours() <= 40 ) // no overtime 48 return getWage() * getHours(); 49 else 50 return 40 * getWage() + ( getHours() - 40 ) * getWage() * 1.5; 51 } // end method getPaymentAmount 52

53 // return String representation of HourlyEmployee object 54 public String toString() 55 {

56 return String.format( "hourly employee: %s\n%s: $%,.2f ; %s: %,.2f", 57 super.toString(), "hourly wage", getWage(), 58 "hours worked", getHours() ); 59 } // end method toString 60 } // end class HourlyEmployee

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1 // Lab Exercise 2: CommissionEmployee.java 2 // CommissionEmployee class extends Employee, which implements Payable. 3

4 public class CommissionEmployee extends Employee 5 {

6 private double grossSales; // gross weekly sales 7 private double commissionRate; // commission percentage 8

9 // f ive-argument constructor 10 public CommissionEmployee( String first, String last, String ssn, 11 double sales, double rate ) 12 {

13 super( first, last, ssn ); 14 setGrossSales( sales ); 15 setCommissionRate( rate ); 16 } // end five-argument CommissionEmployee constructor 17

18 // set commission rate 19 public void setCommissionRate( double rate ) 20 {

21 commissionRate = ( rate > 0.0 && rate < 1.0 ) ? rate : 0.0; 22 } // end method setCommissionRate 23


30 // set gross sales amount 31 public void setGrossSales( double sales ) 32 { 33 grossSales = ( sales < 0.0 ) ? 0.0 : sales; 34 } // end method setGrossSales

35 36 // return gross sales amount 37 public double getGrossSales() 38 { 39 return grossSales; 40 } // end method getGrossSales 41

42 // calculate earnings; implement interface Payable method not 43 // implemented by superclass Employee 44 public double getPaymentAmount() 45 { 46 return getCommissionRate() * getGrossSales(); 47 } // end method getPaymentAmount 48

49 // return String representation of CommissionEmployee object 50 public String toString() 51 { 52 return String.format( "%s: %s\n%s: $%,.2f; %s: %.2f", 53 "commission employee", super.toString(), 54 "gross sales", getGrossSales(), 55 "commission rate", getCommissionRate() ); 56 } // end method toString 57 } // end class CommissionEmployee

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1 // Lab Exercise 2: BasePlusCommissionEmployee.java 2 // BasePlusCommissionEmployee class extends CommissionEmployee.

3


8 // six-argument constructor 9 public BasePlusCommissionEmployee( String first, String last, 10 String ssn, double sales, double rate, double salary ) 11 {

12 super( first, last, ssn, sales, rate ); 13 setBaseSalary( salary ); // validate and store base salary 14 } // end six-argument BasePlusCommissionEmployee constructor 15

16 // set base salary 17 public void setBaseSalary( double salary ) 18 { 19 baseSalary = ( salary < 0.0 ) ? 0.0 : salary; // non-negative 20 } // end method setBaseSalary 21

22 // return base salary 23 public double getBaseSalary() 24 { 25 return baseSalary; 26 } // end method getBaseSalary 27

28 // calculate earnings; override CommissionEmployee implementation of 29 // interface Payable method 30 public double getPaymentAmount() 31 {

32 return getBaseSalary() + super.getPaymentAmount(); 33 } // end method getPaymentAmount 34

35 // return String representation of BasePlusCommissionEmployee object 36 public String toString() 37 { 38 return String.format( "%s %s; %s: $%,.2f", 39 "base-salaried", super.toString(), 40 "base salary", getBaseSalary() ); 41 } // end method toString 42 } // end class BasePlusCommissionEmployee

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1 // Lab Exercise 2: PayableInterfaceTest.java 2 // Tests interface Payable. 3

4 public class PayableInterfaceTest 5 { 6 public static void main( String args[] ) 7 { 8 // create six-element Payable array

9 Payable payableObjects[] = new Payable[ 6 ]; 10

11 // populate array with objects that implement Payable 12 payableObjects[ 0 ] = new Invoice( "01234", "seat", 2, 375.00 ); 13 payableObjects[ 1 ] = new Invoice( "56789", "tire", 4, 79.95 ); 14 payableObjects[ 2 ] = 15 new SalariedEmployee( "John", "Smith", "111-11-1111", 800.00 ); 16 payableObjects[ 3 ] = 17 new HourlyEmployee( "Karen", "Price", "222-22-2222", 16.75, 40 ); 18 payableObjects[ 4 ] = 19 new CommissionEmployee( 20 "Sue", "Jones", "333-33-3333", 10000, .06 ); 21 payableObjects[ 5 ] = 22 new BasePlusCommissionEmployee(

23 "Bob", "Lewis", "444-44-4444", 5000, .04, 300 ); 24

25 System.out.println( 26 "Invoices and Employees processed polymorphically:\n" ); 27

28 // generically process each element in array payableOb jects 29 for ( Payable currentPayable : payableObjects ) 30 { 31 // output currentPayable and its appropriate payment amount 32 System.out.printf( "%s \n", currentPayable.toString() ); 33

34 if ( currentPayable instanceof BasePlusCommissionEmployee ) 35 { 36 // downcast Payable reference to 37 // BasePlusCommissionEmployee reference 38 BasePlusCommissionEmployee employee = 39 ( BasePlusCommissionEmployee ) currentPayable; 40

41 double oldBaseSalary = employee.getBaseSalary(); 42 employee.setBaseSalary( 1.10 * oldBaseSalary ); 43 System.out.printf( 44 "new base salary with 10%% increase is: $%,.2f\n", 45 employee.getBaseSalary() ); 46 } // end if 47

48 System.out.printf( "%s: $%,.2f\n\n", 49 "payment due", currentPayable.getPaymentAmount() ); 50 } // end f or 51 } // end main

52 } // end class PayableInterfaceTest

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Problem-Solving Tips

1. Every class that implements interface Payable must declare a method called getPaymentAmount.

2. Class BasePlusCommissionEmployee must use its superclass’s getPaymentAmount method along with its own base salary to calculate its total earnings.

3. Use the instanceof operator in PayableInterfaceTest to determine whether each object is a Base-

PlusCommissionEmployee object. 4. If you have any questions as you proceed, ask your lab instructor for assistance.

Follow-Up Question and Activity

1. Discuss the benefits and disadvantages of extending an abstract class vs. implementing an interface.

A benefit of an abstract class is that you can declare the instance variables and methods that are required by allclasses in a hierarchy. Subclasses can then enhance the existing instance variables and methods inherited fromthe abstract class and override existing methods as necessary. This reduces the amount of code that must bewritten to create each new class in the hierarchy. This benefit of abstract classes is a disadvantage of inter-faces, which are not allowed to provide any method implementations or instance variables. Thus, any class thatimplements an interface must define all the instance variables and methods necessary to properly satisfy the

requirements of the interface. A benefit of interfaces is that any class can implement an interface such that objects of that class can then be processed in a polymorphic program that uses variables of the interface type. This is particularly useful forextending existing systems. A disadvantage of abstract classes (and classes in general) is that a class can extend only one other class at a time.However, a class can implement multiple interfaces.

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Lab Exercises:

Lab Exercise 3 — Debugging

The program in this section does not compile. Fix all the syntax errors so that the program will compile success-fully. Once the program compiles, execute the program, and compare the output with the sample output; theneliminate any logic errors that may exist. The sample output demonstrates what the program’s output should beonce the pr ogram’s code is corrected. The source code is available at www.pearsonhighered.com/deitel.

Sample Output

Point: [7, 11] Circle: Center = [22, 8]; Radius = 3.500000 Cylinder: Center = [10, 10]; Radius = 3.300000; Height = 10.000000

Point: [7, 11]Area = 0.00

Volume = 0.00

Circle: Center = [22, 8]; Radius = 3.500000 Area = 38.48 Volume = 0.00

Cylinder: Center = [10, 10]; Radius = 3.300000; Height = 10.000000 Area = 275.77 Volume = 342.12

Broken Code

1 // Shape.java 2 // Definition of interface Shape 3

4 public interface Shape 5 { 6 public abstract String getName(); // return shape name 7 } // end interface Shape









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1 // Point.java 2 // Definition of class Point 3

4 public class Point implements Shape 5 { 6 protected int x, y; // coordinates of the Point 7

8 // no-argument constructor 9 public Point() 10 { 11 setPoint( 0, 0 ); 12 }

13

14 // constructor 15 public Point( int xCoordinate, int yCoordinate ) 16 { 17 setPoint( xCoordinate, yCoordinate ); 18 } 19

20 // Set x and y coordinates of Point 21 public void setPoint( int xCoordinate, int yCoordinate )

22 { 23 x = xCoordinate; 24 y = yCoordinate; 25 } 26

27 // get x coordinate 28 public int getX() 29 { 30 return x; 31 } 32

33 // get y coordinate 34 public int getY() 35 {

36 return y; 37 } 38

39 // convert point into String representation 40 public String toString() 41 { 42 return String.format( "[%d, %d]", x, y ); 43 } 44

45 // calculate area 46 public double area() 47 { 48 return 0.0; 49 } 50

51 // calculate volume 52 public double volume() 53 { 54 return 0.0; 55 } 56

57 // return shape name 58 public String getName() 59 { 60 return "Point"; 61 } 62 } // end class Point

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1 // Circle.java 2 // Definition of class Circle 3

4 public class Circle extends Point

5 { 6 protected double radius;

7

8 // no-argument constructor 9 public Circle() 10 { 11 // implicit call to superclass constructor here 12 setRadius( 0 ); 13 } 14

15 // constructor 16 public Circle( double circleRadius, int xCoordinate, int yCoordinate ) 17 { 18 super( xCoordinate, yCoordinate ); // call superclass constructor 19

20 setRadius( circleRadius ); 21 } 22

23 // set radius of Circle 24 public void setRadius( double circleRadius ) 25 { 26 radius = ( circleRadius >= 0 ? circleRadius : 0 ); 27 } 28

29 // get radius of Circle 30 public double getRadius() 31 { 32 return radius; 33 }

34 35 // calculate area of Circle 36 public double area() 37 { 38 return Math.PI * radius * radius; 39 } 40

41 // convert Circle to a String represention 42 public String toString() 43 { 44 return String.format( "Center = %s; Radius = %f", 45 super.toString(), radius ); 46 } 47

48 // return shape name 49 public String getName() 50 { 51 return "Circle"; 52 } 53 } // end class Circle

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1 // Cylinder.java 2 // Definition of class Cylinder. 3

4 public class Cylinder extends Circle 5 { 6 protected double height; // height of Cylinder

7

8 // no-argument constructor 9 public Cylinder() 10 { 11 // implicit call to superclass constructor here 12 setHeight( 0 ); 13 } 14

15 // constructor 16 public Cylinder( double cylinderHeight, double cylinderRadius, 17 int xCoordinate, int yCoordinate ) 18 { 19 // call superclass constructor 20 super( cylinderRadius, xCoordinate, yCoordinate ); 21

22 setHeight( cylinderHeight ); 23 } 24

25 // set height of Cylinder 26 public void setHeight( double cylinderHeight ) 27 { 28 height = ( cylinderHeight >= 0 ? cylinderHeight : 0 ); 29 } 30

31 // get height of Cylinder 32 public double getHeight() 33 { 34 return height; 35 }

36

37 // calculate area of Cylinder (i.e., surface area) 38 public double area() 39 { 40 return 2 * super.area() + 2 * Math.PI * radius * height; 41 } 42

43 // calculate volume of Cylinder 44 public double volume() 45 { 46 return super.area() * height; 47 } 48

49 // convert Cylinder to a String representation 50 public String toString()

51 { 52 return String.format( "%s; Height = %f", 53 super.toString(), height ); 54 } 55

56 // return shape name 57 public String getName() 58 { 59 return "Cylinder"; 60 } 61 } // end class Cylinder

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1 // Test.java 2 // Test Point, Circle, Cylinder hierarchy with interface Shape. 3

4 public class Test 5 {

6 // test Shape hierarchy 7 public static void main( String args[] ) 8 { 9 // create shapes 10 Point point = new Point( 7, 11 ); 11 Circle circle = new Circle( 3.5, 22, 8 ); 12 Cylinder cylinder = new Cylinder( 10, 3.3, 10, 10 ); 13

14 Cylinder arrayOfShapes[] = new Cylinder[ 3 ]; // create Shape array 15

16 // aim arrayOfShapes[ 0 ] at subclass Point object 17 arrayOfShapes[ 0 ] = ( Cylinder ) point; 18

19 // aim arrayOfShapes[ 1 ] at subclass Circle object 20 arrayOfShapes[ 1 ] = ( Cylinder ) circle;

21

22 // aim arrayOfShapes[ 2 ] at subclass Cylinder object 23 arrayOfShapes[ 2 ] = ( Cylinder ) cylinder; 24

25 // get name and String representation of each shape 26 System.out.printf( "%s: %s\n%s: %s\n%s: %s\n", point.getName(), 27 point, circle.getName(), circle, cylinder.getName(), cylinder ); 28

29 // get name, area and volume of each shape in arrayOfShapes 30 for ( Shape shape : arrayOfShapes ) 31 { 32 System.out.printf( "\n\n%s: %s\nArea = %.2f\nVolume = %.2f\n", 33 shape.getName(), shape, shape.area(), shape.volume() ); 34 } // end f or

35 } // end main 36 } // end class Test

Solution

1 // Shape.java 2 // Definition of interface Shape 3

4 public interface Shape 5 { 6 public abstract double area(); // calculate area 7 public abstract double volume(); // calculate volume 8 public abstract String getName(); // return shape name

9 } // end interface Shape

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1 // Point.java 2 // Definition of class Point 3

4 public class Point implements Shape 5 {

6 protected int x, y; // coordinates of the Point 7

8 // no-argument constructor 9 public Point() 10 { 11 setPoint( 0, 0 ); 12 } 13

14 // constructor 15 public Point( int xCoordinate, int yCoordinate ) 16 { 17 setPoint( xCoordinate, yCoordinate ); 18 } 19

20 // Set x and y coordinates of Point

21 public void setPoint( int xCoordinate, int yCoordinate ) 22 { 23 x = xCoordinate; 24 y = yCoordinate; 25 } 26

27 // get x coordinate 28 public int getX() 29 { 30 return x; 31 } 32

33 // get y coordinate 34 public int getY()

35 { 36 return y; 37 } 38

39 // convert point into String representation 40 public String toString() 41 { 42 return String.format( "[%d, %d]", x, y ); 43 } 44

45 // calculate area 46 public double area() 47 { 48 return 0.0; 49 }

50

51 // calculate volume 52 public double volume() 53 { 54 return 0.0; 55 } 56

57 // return shape name 58 public String getName() 59 { 60 return "Point"; 61 } 62 } // end class Point

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1 // Circle.java 2 // Definition of class Circle 3

4 public class Circle extends Point 5 {

6 protected double radius; 7

8 // no-argument constructor 9 public Circle() 10 { 11 // implicit call to superclass constructor here 12 setRadius( 0 ); 13 } 14

15 // constructor 16 public Circle( double circleRadius, int xCoordinate, int yCoordinate ) 17 { 18 super( xCoordinate, yCoordinate ); // call superclass constructor 19

20 setRadius( circleRadius ); 21 } 22

23 // set radius of Circle 24 public void setRadius( double circleRadius ) 25 { 26 radius = ( circleRadius >= 0 ? circleRadius : 0 ); 27 } 28

29 // get radius of Circle 30 public double getRadius() 31 { 32 return radius; 33 } 34

35 // calculate area of Circle 36 public double area() 37 { 38 return Math.PI * radius * radius; 39 } 40

41 // convert Circle to a String represention 42 public String toString() 43 { 44 return String.format( "Center = %s; Radius = %f", 45 super.toString(), radius ); 46 } 47

48 // return shape name 49 public String getName() 50 { 51 return "Circle"; 52 } 53 } // end class Circle

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1 // Cylinder.java 2 // Definition of class Cylinder. 3

4 public class Cylinder extends Circle 5 { 6 protected double height; // height of Cylinder 7

8 // no-argument constructor

9 public Cylinder() 10 { 11 // implicit call to superclass constructor here 12 setHeight( 0 ); 13 } 14

15 // constructor 16 public Cylinder( double cylinderHeight, double cylinderRadius, 17 int xCoordinate, int yCoordinate ) 18 { 19 // call superclass constructor 20 super( cylinderRadius, xCoordinate, yCoordinate ); 21

22 setHeight( cylinderHeight );

23 } 24

25 // set height of Cylinder 26 public void setHeight( double cylinderHeight ) 27 { 28 height = ( cylinderHeight >= 0 ? cylinderHeight : 0 ); 29 } 30

31 // get height of Cylinder 32 public double getHeight() 33 { 34 return height; 35 } 36

37 // calculate area of Cylinder (i.e., surface area)

38 public double area() 39 { 40 return 2 * super.area() + 2 * Math.PI * radius * height; 41 } 42

43 // calculate volume of Cylinder 44 public double volume() 45 { 46 return super.area() * height; 47 } 48

49 // convert Cylinder to a String representation 50 public String toString() 51 {

52 return String.format( "%s; Height=

%f", 53 super.toString(), height ); 54 } 55

56 // return shape name 57 public String getName() 58 {

59 return "Cylinder"; 60 } 61 } // end class Cylinder

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1 // Test.java 2 // Test Point, Circle, Cylinder hierarchy with interface Shape. 3

4 public class Test 5 { 6 // test Shape hierarchy

7 public static void main( String args[] ) 8 { 9 // create shapes 10 Point point = new Point( 7, 11 ); 11 Circle circle = new Circle( 3.5, 22, 8 ); 12 Cylinder cylinder = new Cylinder( 10, 3.3, 10, 10 ); 13

14 Shape arrayOfShapes[] = new Shape[ 3 ]; // create Shape array 15

16 // aim arrayOfShapes[ 0 ] at subclass Point object 17 arrayOfShapes[ 0 ] = point; 18

19 // aim arrayOfShapes[ 1 ] at subclass Circle object 20 arrayOfShapes[ 1 ] = circle;

21 22 // aim arrayOfShapes[ 2 ] at subclass Cylinder object 23 arrayOfShapes[ 2 ] = cylinder; 24

25 // get name and String representation of each shape 26 System.out.printf( "%s: %s\n%s: %s\n%s: %s\n", point.getName(), 27 point, circle.getName(), circle, cylinder.getName(), cylinder ); 28

29 // get name, area and volume of each shape in arrayOfShapes 30 for ( Shape shape : arrayOfShapes ) 31 { 32 System.out.printf( "\n\n%s: %s\nArea = %.2f\nVolume = %.2f\n", 33 shape.getName(), shape, shape.area(), shape.volume() ); 34 } // end f or 35 } // end main

36 } // end class Test

List of Errors

Shape.java: The Shape interface must declare public abstract methods area and volume. Test.java, line 14: The array should be of type Shape so that the array elements can refer to Point,

Circle and Cylinder objects for polymorphic processing. Test.java, line 17: Once the array is changed to type Shape, it is not necessary to cast point to a dif-

ferent type — a Point object can always be assigned to a Shape variable based on the hierarchy defined inthis exercise.

Test.java, line 20: Once the array is changed to type Shape, it is not necessary to cast circle to a dif-ferent type — a Circle object can always be assigned to a Shape variable based on the hierarchy defined in

this exercise. Test.java, line 23: The cast operation is unnecessary — a Cylinder object can always be assigned to a

Shape variable based on the hierarchy defined in this exercise.

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Postlab Activities

Coding Exercises

These coding exercises reinforce the lessons learned in the lab and provide additional programming experienceoutside the classroom and laboratory environment. They serve as a review after you have successfully completedthe Prelab Activities and Lab Exerci se s.

For each of the following pr obl em s , write a program or a program segment that performs the specified action.

1. Write an empty class declaration for an abstract class called Shape.

1 // Shape.java 2 // Shape class declaration. 3

4 public abstract class Shape 5 {

6 } // end class Shape

2. In the class from Coding Exer ci se 1, create a protected instance variable shapeName of type String, and write

an accessor method getName for obtaining its value.


4 public abstract class Shape 5 { 6 protected String shapeName; 7

8 public String getName()

9 { 10 return shapeName; 11 } 12 } // end class Shape

3. In the class of Coding Exer ci se 2, define an abstract method getArea that returns a double representationof a specific shape’s area. Subclasses of this class must implement getArea to calculate a specific shape’s area.


4 public abstract class Shape 5 {

6 protected String shapeName; 7

8 // abstract getArea method must be implemented by concrete subclasses 9 public abstract double getArea(); 10

11 public String getName() 12 { 13 return shapeName; 14 } 15 } // end class Shape

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4. Define a class Square that inherits from class Shape from Coding Exer ci se 3; it should contain an instance

variable side, which represents the length of a side of the square. Provide a constructor that takes oneargument representing the side of the square and sets the side variable. Ensure that the side is greater than

or equal to 0. The constructor should set the inherited shapeName variable to the string "Square".

1 // Square.java

2 // Definition of class Square. 3

4 public class Square extends Shape 5 { 6 private double side; 7

8 // constructor 9 public Square( double s ) 10 { 11 side = ( s < 0 ? 0 : s ); 12 shapeName = "Square"; 13 } 14 } // end class Square

5. The Square class from Coding Exerci se 4 should implement the getArea method of its abstract su perclass;

this implementation should compute the area of the square and return the result.

1 // Square.java 2 // Definition of class Square. 3

4 public class Square extends Shape 5 { 6 private double side; 7

8 // constructor 9 public Square( double s ) 10 {

11 side = ( s < 0 ? 0 : s ); 12 shapeName = "Square"; 13 } 14

15 // return the area of a Square 16 public double getArea() 17 { 18 return side * side; 19 } 20 } // end class Square

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8. Write an application that tests the Square and Rectangle classes from Coding Exer ci se s 5 and 7 , respectively.

Create an array of type Shape that holds an instance of Square and an instance of Rectangle. The program

should polymorphically compute and display the areas of both objects. Allow a user to enter the values for the

side of the square and the length and width of the rectangle.

1 // TestArea.java

2 import java.util.Scanner; 3

4 public class TestArea 5 { 6 public static void main( String args[] ) 7 { 8 Scanner input = new Scanner( System.in ); 9

10 System.out.print( "Input the side of the square: " ); 11 double side = input.nextDouble(); 12

13 System.out.print( "Input the length of the rectangle: " ); 14 double length = input.nextDouble(); 15

16 System.out.print( "Input the width of the rectangle: " );

17 double width = input.nextDouble(); 18

19 Shape arrayOfShapes[] = new Shape[ 2 ]; 20 arrayOfShapes[ 0 ] = new Square( side ); 21 arrayOfShapes[ 1 ] = new Rectangle( length, width ); 22

23 for ( Shape shape : arrayOfShapes ) 24 System.out.printf( "The %s has an area of %.2f\n", shape.getName(), 25 shape.getArea() ); 26 } // end main 27 } // end class TestArea

Input the side of the square: 10.5 Input the length of the rectangle: 2.5 Input the width of the rectangle: 3.5 The Square has an area of 110.25 The Rectangle has an area of 8.75

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Postlab Activities

Programming Challenges

The Programming C hall en ge s are more involved than the Coding Exerci se s and may require a significant amount of

time to complete. Write a Java program for each of the problems in this section. The answers to these problems areavailable at www.pearsonhighered.com/deitel. Pseudocode, hints or sample outputs are provided for each problem to aid you in your programming.

9. (Payroll System M odification ) Modify the payroll system of Figs. 10.4 – 10.9 to include private instance

variable birthDate in class Employee. Use class Date of Fig. 8.7 to represent an employee’s birthday. Add

get methods to class Date and replace method toDateString with method toString. Assume that payroll is

processed once per month. Create an array of Employee variables to store references to the various

employee objects. In a loop, calculate the payroll for each Employee (polymorphically), and add a $100.00

bonus to the person’s payroll amount if the current month is the month in which the Employee’s birthdayoccurs.

Hint: • Your output should appear as follows:

Date object constructor for date 6/15/1944 Date object constructor for date 12/29/1960 Date object constructor for date 9/8/1954 Date object constructor for date 3/2/1965 Employees processed individually:

salaried employee: John Smith social security number: 111-11-1111 birth date: 6/15/1944 weekly salary: $800.00

earned: $800.00

hourly employee: Karen Price social security number: 222-22-2222 birth date: 12/29/1960 hourly wage: $16.75; hours worked: 40.00 earned: $670.00

commission employee: Sue Jones socialsecurity number: 333-33-3333 birth date: 9/8/1954 gross sales: $10,000.00; commission rate: 0.06earned: $600.00

base-salaried commission employee: Bob Lewissocial security number: 444-44-4444

birth date: 3/2/1965 gross sales: $5,000.00; commission rate: 0.04; base salary: $300.00 earned: $500.00

Enter the current month (1 - 12): 3

(continued next pa ge... )




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Employees processed polymorphically:

salaried employee: John Smith social security number: 111-11-1111 birth date: 6/15/1944 weekly salary: $800.00

earned $800.00

hourly employee: Karen Price social security number: 222-22-2222 birth date: 12/29/1960 hourly wage: $16.75; hours worked: 40.00 earned $670.00

commission employee: Sue Jones socialsecurity number: 333-33-3333 birth date: 9/8/1954 gross sales: $10,000.00; commission rate: 0.06 earned $600.00

base-salaried commission employee: Bob Lewissocial security number: 444-44-4444 birth date: 3/2/1965 gross sales: $5,000.00; commission rate: 0.04; base salary: $300.00 new base salary with 10% increase is: $330.00 earned $530.00 plus $100.00 birthday bonus

Employee 0 is a SalariedEmployeeEmployee 1 is a HourlyEmployeeEmployee 2 is a CommissionEmployee Employee 3 is a BasePlusCommissionEmployee

Solution

1 // Programming Challenge 1: Employee.java

2 // Employee abstract superclass. 3

4 public abstract class Employee 5 { 6 private String firstName; 7 private String lastName; 8 private String socialSecurityNumber; 9 private Date birthDate; 10

11 // six-argument constructor 12 public Employee( String first, String last, String ssn, 13 int month, int day, int year ) 14 { 15 f irstName = first;

16 lastName = last; 17 socialSecurityNumber = ssn; 18 birthDate = new Date( month, day, year ); 19 } // end six-argument Employee constructor 20

21 // set first name 22 public void setFirstName( String first ) 23 { 24 f irstName = first;

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1 // Programming Challenge 1: Date. java 2 // Date class declaration with get methods added. 3

4 public class Date 5 { 6 private int month; // 1-12

7 private int day; // 1-31 based on month 8 private int year; // any year 9

10 // constructor: call checkMonth to confirm proper value f or month; 11 // call checkDay to confirm proper value for day 12 public Date( int theMonth, int theDay, int theYear ) 13 { 14 month = checkMonth( theMonth ); // validate month 15 year = theYear; // could validate year 16 day = checkDay( theDay ); // validate day 17

18 System.out.printf( 19 "Date object constructor for date %s\n", toString() ); 20 } // end Date constructor

21

22 // utility method to confirm proper month value 23 private int checkMonth( int testMonth ) 24 { 25 if ( testMonth > 0 && testMonth <= 12 ) // validate month 26 return testMonth; 27 else // month is invalid 28 { 29 System.out.printf( "Invalid month (%d) set to 1.\n", testMonth ); 30 return 1; // maintain ob ject in consistent state 31 } // end else 32 } // end method checkMonth 33

34 // utility method to confirm proper day value based on month and year 35 private int checkDay( int testDay )

36 { 37 int daysPerMonth[] = 38 { 0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 }; 39

40 // check if day in range for month 41 if ( testDay > 0 && testDay <= daysPerMonth[ month ] ) 42 return testDay; 43

44 // check f or leap year 45 if ( month == 2 && testDay == 29 && ( year % 400 == 0 || 46 ( year % 4 == 0 && year % 100 != 0 ) ) ) 47 return testDay; 48

49 System.out.printf( "Invalid day (%d) set to 1.\n", testDay );

50

51 return 1; // maintain object in consistent state 52 } // end method checkDay 53

54 // return day 55 public int getDay() 56 { 57 return day; 58 } // end method getDay

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59

60 // return month 61 public int getMonth() 62 { 63 return month; 64 } // end method getMonth

65 66 // return year 67 public int getYear() 68 { 69 return year; 70 } // end method getYear 71

72 // return a String of the form month/day/year 73 public String toString() 74 { 75 return String.format( "%d/%d/%d", month, day, year ); 76 } // end method toString 77 } // end class Date

1 // Programming Challenge 1: SalariedEmployee.java 2 // SalariedEmployee class derived from Employee. 3

4 public class SalariedEmployee extends Employee 5 { 6 private double weeklySalary; 7

8 // seven-argument constructor 9 public SalariedEmployee( String first, String last, String ssn, 10 int month, int day, int year, double salary ) 11 { 12 super( first, last, ssn, month, day, year ); 13 setWeeklySalary( salary ); 14 } // end seven-argument SalariedEmployee constructor 15

16 // set salary 17 public void setWeeklySalary( double salary ) 18 { 19 weeklySalary = salary < 0.0 ? 0.0 : salary; 20 } // end method setWeeklySalary 21

22 // return salary 23 public double getWeeklySalary() 24 { 25 return weeklySalary; 26 } // end method getWeeklySalary 27

28 // calculate earnings; override abstract method earnings in Employee

29 public double earnings() 30 { 31 return getWeeklySalary(); 32 } // end method earnings 33

34 // return String representation of SalariedEmployee object 35 public String toString() 36 {

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37 return String.format( "salaried employee: %s\n%s: $%,.2f", 38 super.toString(), "weekly salary", getWeeklySalary() ); 39 } // end method toString 40 } // end class SalariedEmployee

1 // Programming Challenge 1: HourlyEmployee.java 2 // HourlyEmployee class derived f rom Employee. 3

4 public class HourlyEmployee extends Employee 5 { 6 private double wage; // wage per hour 7 private double hours; // hours worked f or week 8

9 // eight-argument constructor 10 public HourlyEmployee( String first, String last, String ssn, 11 int month, int day, int year, 12 double hourlyWage, double hoursWorked )

13 { 14 super( first, last, ssn, month, day, year ); 15 setWage( hourlyWage ); 16 setHours( hoursWorked ); 17 } // end eight-argument HourlyEmployee constructor 18

19 // set wage 20 public void setWage( double hourlyWage ) 21 { 22 wage = hourlyWage < 0.0 ? 0.0 : hourlyWage; 23 } // end method setWage 24

25 // return wage 26 public double getWage()

27 { 28 return wage; 29 } // end method getWage 30


38 // return hours worked 39 public double getHours() 40 { 41 return hours; 42 } // end method getHours 43

44 // calculate earnings; override abstract method earnings in Employee 45 public double earnings() 46 { 47 if ( getHours() <= 40 ) // no overtime 48 return getWage() * getHours(); 49 else 50 return 40 * getWage() + ( getHours() - 40 ) * getWage() * 1.5; 51 } // end method earnings 52

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53 // return String representation of HourlyEmployee object 54 public String toString() 55 { 56 return String.format( "hourly employee: %s\n%s: $%,.2f ; %s: %,.2f", 57 super.toString(), "hourly wage", getWage(), 58 "hours worked", getHours() ); 59 } // end method toString

60 } // end class HourlyEmployee

1 // Programming Challenge 1: CommissionEmployee.java 2 // CommissionEmployee class derived from Employee. 3


9 // eight-argument constructor 10 public CommissionEmployee( String first, String last, String ssn, 11 int month, int day, int year, double sales, double rate )

12 { 13 super( first, last, ssn, month, day, year ); 14 setGrossSales( sales ); 15 setCommissionRate( rate ); 16 } // end eight-argument CommissionEmployee constructor 17



30 // set gross sales amount 31 public void setGrossSales( double sales ) 32 { 33 grossSales = sales < 0.0 ? 0.0 : sales; 34 } // end method setGrossSales 35

36 // return gross sales amount 37 public double getGrossSales() 38 { 39 return grossSales; 40 } // end method getGrossSales

41 42 // calculate earnings; override abstract method earnings in Employee 43 public double earnings() 44 { 45 return getCommissionRate() * getGrossSales(); 46 } // end method earnings 47

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48 // return String representation of CommissionEmployee object 49 public String toString() 50 { 51 return String.format( "%s: %s\n%s: $%,.2f; %s: %.2f", 52 "commission employee", super.toString(), 53 "gross sales", getGrossSales(),

54 "commission rate", getCommissionRate() ); 55 } // end method toString 56 } // end class CommissionEmployee

1 // Programming Challenge 1: BasePlusCommissionEmployee.java 2 // BasePlusCommissionEmployee class derived from CommissionEmployee. 3


8 // nine-argument constructor 9 public BasePlusCommissionEmployee( String first, String last,

10 String ssn, int month, int day, int year, 11 double sales, double rate, double salary ) 12 { 13 super( first, last, ssn, month, day, year, sales, rate ); 14 setBaseSalary( salary ); 15 } // end nine-argument BasePlusCommissionEmployee constructor 16

17 // set base salary 18 public void setBaseSalary( double salary ) 19 { 20 baseSalary = salary < 0.0 ? 0.0 : salary; // non-negative 21 } // end method setBaseSalary 22

23 // return base salary 24 public double getBaseSalary() 25 { 26 return baseSalary; 27 } // end method getBaseSalary 28

29 // calculate earnings; override method earnings in CommissionEmployee 30 public double earnings() 31 { 32 return getBaseSalary() + super.earnings(); 33 } // end method earnings 34

35 // return String representation of BasePlusCommissionEmployee object 36 public String toString() 37 { 38 return String.format( "%s %s; %s: $%,.2f",

39 "base-salaried", super.toString(), 40 "base salary", getBaseSalary() ); 41 } // end method toString 42 } // end class BasePlusCommissionEmployee

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1 // Programming Challenge 1: PayrollSystemTest.java 2 // Employee hierarchy test program. 3 import java.util.Scanner; // program uses Scanner to obtain user input 4

5 public class PayrollSystemTest 6 {

7 public static void main( String args[] ) 8 { 9 // create subclass objects 10 SalariedEmployee salariedEmployee = 11 new SalariedEmployee( 12 "John", "Smith", "111-11-1111", 6, 15, 1944, 800.00 ); 13 HourlyEmployee hourlyEmployee = 14 new HourlyEmployee( 15 "Karen", "Price", "222-22-2222", 12, 29, 1960, 16.75, 40 ); 16 CommissionEmployee commissionEmployee = 17 new CommissionEmployee( 18 "Sue", "Jones", "333-33-3333", 9, 8, 1954, 10000, .06 ); 19 BasePlusCommissionEmployee basePlusCommissionEmployee = 20 new BasePlusCommissionEmployee(

21 "Bob", "Lewis", "444-44-4444", 3, 2, 1965, 5000, .04, 300 ); 22

23 System.out.println( "Employees processed individually:\n" ); 24

25 System.out.printf( "%s\n%s: $%,.2f\n\n", 26 salariedEmployee, "earned", salariedEmployee.earnings() ); 27 System.out.printf( "%s\n%s: $%,.2f\n\n", 28 hourlyEmployee, "earned", hourlyEmployee.earnings() ); 29 System.out.printf( "%s\n%s: $%,.2f\n\n", 30 commissionEmployee, "earned", commissionEmployee.earnings() ); 31 System.out.printf( "%s\n%s: $%,.2f\n\n", 32 basePlusCommissionEmployee, 33 "earned", basePlusCommissionEmployee.earnings() ); 34

35 // create four-element Employee array

36 Employee employees[] = new Employee[ 4 ]; 37

38 // initialize array with Employees 39 employees[ 0 ] = salariedEmployee; 40 employees[ 1 ] = hourlyEmployee; 41 employees[ 2 ] = commissionEmployee; 42 employees[ 3 ] = basePlusCommissionEmployee; 43

44 Scanner input = new Scanner( System.in ); // to get current month 45 int currentMonth; 46

47 // get and validate current month 48 do 49 {

50 System.out.print( "Enter the current month (1 - 12): " ); 51 currentMonth = input.nextInt(); 52 System.out.println(); 53 } while ( ( currentMonth < 1 ) || ( currentMonth > 12 ) ); 54


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57 // generically process each element in array employees 58 for ( Employee currentEmployee : employees ) 59 { 60 System.out.println( currentEmployee ); // invokes toString 61

62 // determine whether element is a BasePlusCommissionEmployee 63 if ( currentEmployee instanceof BasePlusCommissionEmployee ) 64 { 65 // downcast Employee reference to 66 // BasePlusCommissionEmployee reference 67 BasePlusCommissionEmployee employee = 68 ( BasePlusCommissionEmployee ) currentEmployee; 69

70 double oldBaseSalary = employee.getBaseSalary(); 71 employee.setBaseSalary( 1.10 * oldBaseSalary ); 72 System.out.printf( 73 "new base salary with 10%% increase is: $%,.2f\n", 74 employee.getBaseSalary() ); 75 } // end if 76

77 // if month of employee's birthday, add $100 to salary 78 if ( currentMonth == currentEmployee.getBirthDate().getMonth() ) 79 System.out.printf( 80 "earned $%,.2f %s\n\n", currentEmployee.earnings(), 81 "plus $100.00 birthday bonus" ); 82 else 83 System.out.printf( 84 "earned $%,.2f\n\n", currentEmployee.earnings() ); 85 } // end f or 86

87 // get type name of each ob ject in employees array 88 for ( int j = 0; j < employees.length; j++ ) 89 System.out.printf( "Employee %d is a %s\n", j, 90 employees[ j ].getClass().getName() );

91 } // end main 92 } // end class PayrollSystemTest

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10. (Shape Hierarchy) Implement the Shape hierarchy shown in Fig. 9.3 of Java How to Program. Each

TwoDimensionalShape should contain method getArea to calculate the area of the two-dimensional shape.

Each ThreeDimensionalShape should have methods getArea and getVolume to calculate the surface area and

volume, respectively, of the three-dimensional shape. Create a program that uses an array of Shape

references to objects of each concrete class in the hierarchy. The program should print a text description ofthe object to which each array element refers. Also, in the loop that processes all the shapes in the array,

determine whether each shape is a TwoDimensionalShape or a ThreeDimensionalShape. If a shape is aTwoDimensionalShape, display its area. If a shape is a ThreeDimensionalShape, display its area and volume.

Hint:

• Your output should appear as follows:

Circle: [22, 88] radius: 4 Circle's area is 50

Square: [71, 96] side: 10 Square's area is 100

Sphere: [8, 89] radius: 2 Sphere's area is 50

Sphere's volume is 33

Cube: [79, 61] side: 8 Cube's area is 384 Cube's volume is 512

Solution

1 // Programming Challenge 2: Shape.java 2 // Definition of class Shape. 3

4 public abstract class Shape

5 { 6 private int x; // x coordinate 7 private int y; // y coordinate 8

9 // two-argument constructor 10 public Shape( int x, int y ) 11 { 12 this.x = x; 13 this.y = y; 14 } // end two-argument Shape constructor 15

16 // set x coordinate 17 public void setX( int x ) 18 { 19 this.x = x;

20 } // end method setX 21

22 // set y coordinate 23 public void setY( int y ) 24 { 25 this.y = y; 26 } // end method setY

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27

28 // get x coordinate 29 public int getX() 30 { 31 return x; 32 } // end method getX 33

34 // get y coordinate 35 public int getY() 36 { 37 return y; 38 } // end method getY 39

40 // return String representation of Shape object 41 public String toString() 42 { 43 return String.format( "(%d, %d)", getX(), getY() ); 44 } 45

46 // abstract methods 47 public abstract String getName(); 48 } // end class Shape

1 // Programming Challenge 2: TwoDimensionalShape.java 2 // Definition of class TwoDimensionalShape. 3

4 public abstract class TwoDimensionalShape extends Shape 5 { 6 private int dimension1; 7 private int dimension2; 8

9 // f our-argument constructor 10 public TwoDimensionalShape( int x, int y, int d1, int d2 ) 11 { 12 super( x, y ); 13 dimension1 = d1; 14 dimension2 = d2; 15 } // end four-argument TwoDimensionalShape constructor 16

17 // set methods 18 public void setDimension1( int d ) 19 { 20 dimension1 = d; 21 } // end method setDimension1 22

23 public void setDimension2( int d ) 24 { 25 dimension2 = d; 26 } // end method setDimension2

27 28 // get methods 29 public int getDimension1() 30 { 31 return dimension1; 32 } // end method getDimension1 33

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34 public int getDimension2() 35 { 36 return dimension2; 37 } // end method getDimension2 38

39 // abstract method 40 public abstract int getArea();

41 } // end class TwoDimensionalShape

1 // Programming Challenge 2: Circle.java 2 // Definition of class Circle. 3

4 public class Circle extends TwoDimensionalShape 5 { 6 // three-argument constructor 7 public Circle( int x, int y, int radius) 8 {

9 super( x, y, radius, radius ); 10 } // end three-argument Circle constructor 11

12 // overridden methods 13 public String getName() 14 { 15 return "Circle"; 16 } // end method getName 17

18 public int getArea() 19 { 20 return ( int ) 21 ( Math.PI * getRadius() * getRadius() ); 22 } // end method getArea

23 24 // set method 25 public void setRadius( int radius ) 26 { 27 setDimension1( radius ); 28 setDimension2( radius ); 29 } // end method setRadius 30

31 // get method 32 public int getRadius() 33 { 34 return getDimension1(); 35 } // end method getRadius 36

37 public String toString() 38 { 39 return String.format( "%s %s: %d\n", 40 super.toString(), "radius", getRadius() ); 41 } // end method toString 42 } // end class Circle

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1 // Programming Challenge 2: Square.java 2 // Definition of class Square. 3

4 public class Square extends TwoDimensionalShape 5 { 6 // three-argument constructor

7 public Square( int x, int y, int side ) 8 { 9 super( x, y, side, side ); 10 } // end three-argument Square constructor 11

12 // overridden methods 13 public String getName() 14 { 15 return "Square"; 16 } // end method getName 17

18 public int getArea() 19 { 20 return getSide() * getSide(); 21 } // end method getArea

22

23 // set method 24 public void setSide( int side ) 25 { 26 setDimension1( side ); 27 setDimension2( side ); 28 } // end method setSide 29

30 // get method 31 public int getSide() 32 { 33 return getDimension1(); 34 } // end method getSide 35

36 public String toString() 37 { 38 return String.format( "%s %s: %d\n", 39 super.toString(), "side", getSide() ); 40 } // end method toString 41 } // end class Square

1 // Programming Challenge 2: ThreeDimensionalShape.java 2 // Definition of class ThreeDimensionalShape. 3

4 public abstract class ThreeDimensionalShape extends Shape 5 { 6 private int dimension1;

7 private int dimension2; 8 private int dimension3; 9

10 // f ive-argument constructor 11 public ThreeDimensionalShape( 12 int x, int y, int d1, int d2, int d3 ) 13 { 14 super( x, y ); 15 dimension1 = d1;

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16 dimension2 = d2; 17 dimension3 = d3; 18 } // end five-argument ThreeDimensionalShape constructor 19

20 // set methods 21 public void setDimension1( int d )

22 { 23 dimension1 = d; 24 } // end method setDimension1 25

26 public void setDimension2( int d ) 27 { 28 dimension2 = d; 29 } // end method setDimension2 30

31 public void setDimension3( int d ) 32 { 33 dimension3 = d; 34 } // end method setDimension3 35

36 // get methods 37 public int getDimension1()

38 { 39 return dimension1; 40 } // end method getDimension1 41

42 public int getDimension2() 43 { 44 return dimension2; 45 } // end method getDimension2 46

47 public int getDimension3() 48 { 49 return dimension3; 50 } // end method getDimension3

51 52 // abstract methods 53 public abstract int getArea(); 54 public abstract int getVolume(); 55 } // end class ThreeDimensionalShape

1 // Programming Challenge 2: Sphere.java 2 // Definition of class Sphere. 3

4 public class Sphere extends ThreeDimensionalShape 5 { 6 // three-argument constructor 7 public Sphere( int x, int y, int radius)

8 { 9 super( x, y, radius, radius, radius ); 10 } // end three-argument Shape constructor 11

12 // overridden methods 13 public String getName() 14 { 15 return "Sphere"; 16 } // end method getName

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17

18 public int getArea() 19 { 20 return ( int ) ( 4 * Math.PI * getRadius() * getRadius() ); 21 } // end method getArea 22

23 public int getVolume()

24 { 25 return ( int ) ( 4.0 / 3.0 * Math.PI * 26 getRadius() * getRadius() * getRadius() ); 27 } // end method getVolume 28

29 // set method 30 public void setRadius( int radius ) 31 { 32 setDimension1( radius ); 33 setDimension2( radius ); 34 setDimension3( radius ); 35 } // end method setRadius 36

37 // get method 38 public int getRadius()

39 { 40 return getDimension1(); 41 } // end method getRadius 42

43 public String toString() 44 { 45 return String.format( "%s %s: %d\n", 46 super.toString(), "radius", getRadius() ); 47 } // end method toString 48 } // end class Sphere

1 // Programming Challenge 2: Cube. java 2 // Definition of class Cube. 3

4 public class Cube extends ThreeDimensionalShape 5 { 6 // three-argument constructor 7 public Cube( int x, int y, int side ) 8 { 9 super( x, y, side, side, side ); 10 } // end three-argument Cube constructor 11

12 // overridden methods 13 public String getName() 14 { 15 return "Cube"; 16 } // end method getName

17 18 public int getArea() 19 { 20 return ( int ) ( 6 * getSide() * getSide() ); 21 } // end method getArea 22

23 public int getVolume() 24 {

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25 return ( int ) ( getSide() * getSide() * getSide() ); 26 } // end method getVolume 27

28 // set method 29 public void setSide( int side ) 30 { 31 setDimension1( side ); 32 setDimension2( side ); 33 setDimension3( side ); 34 } // end method setSide 35

36 // get method 37 public int getSide() 38 { 39 return getDimension1(); 40 } // end method getSide 41

42 public String toString() 43 {

44 return String.format( "%s %s: %d\n", 45 super.toString(), "side", getSide() ); 46 } // end method toString 47 } // end class Cube

1 // Programming Challenge 2: ShapeTest.java 2 // Program tests the Shape hierarchy. 3

4 public class ShapeTest 5 { 6 // create Shape objects and display their information 7 public static void main( String args[] ) 8 { 9 Shape shapes[] = new Shape[ 4 ]; 10 shapes[ 0 ] = new Circle( 22, 88, 4 ); 11 shapes[ 1 ] = new Square( 71, 96, 10 ); 12 shapes[ 2 ] = new Sphere( 8, 89, 2 ); 13 shapes[ 3 ] = new Cube( 79, 61, 8 ); 14

15 // call method print on all shapes 16 for ( Shape currentShape : shapes ) 17 { 18 System.out.printf( "%s: %s", 19 currentShape.getName(), currentShape ); 20

21 if ( currentShape instanceof TwoDimensionalShape )

22 { 23 TwoDimensionalShape twoDimensionalShape = 24 ( TwoDimensionalShape ) currentShape; 25

26 System.out.printf( "%s's area is %s\n", 27 currentShape.getName(), twoDimensionalShape.getArea() ); 28 } // end if 29

30 if ( currentShape instanceof ThreeDimensionalShape ) 31 { 32 ThreeDimensionalShape threeDimensionalShape = 33 ( ThreeDimensionalShape ) currentShape;

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CPCS 203 Lab sheet 4Student Name:_____________________________ Section:__

34

35 System.out.printf( "%s's area is %s\n", 36 currentShape.getName(), threeDimensionalShape.getArea() ); 37 System.out.printf( "%s's volume is %s\n", 38 currentShape.getName(),

39 threeDimensionalShape.getVolume() ); 40 } // end if 41

42 System.out.println(); 43 } // end f or 44 } // end main 45 } // end class ShapeTest

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