java object oriented programming (oop)

Introduction to

Object-Oriented Programming

Prof. Erwin M. Globio, MSIT Java Training Specialist

http://eglobiotraining.com

Lesson 1

Object Oriented Programming

Model Real World Objects

Encapsulate Data and Function

Java is used for Networking

Has many classes to program

Internet communications

Java-enabled devices

mobile phones

Web pages with additional

animation and functionality

Java servlets

Java is Simple

Derived from C/C++

Simpler than C/C++.

No preprocessors

Pointers were eliminated

Common data structures that use

pointers such as stacks, lists and

trees are available

Java is Robust

Employs strong type checking

Every data structure is defined

and its type is checked during

compilation and runtime

Built-in exception handling

Garbage collection is done

automatically

Java is Dynamic

There are many available Java

resources in the Internet.

Using interfaces

Classes are dynamically loaded.

Java is Secure

System breakers can not gain

access to system resources

the Java bytecode verifier

loaded classes can not access the

file system

a public-key encryption system

(in the future)

Java is Free

Java can be downloaded from the

Internet for FREE

Just visit http://java.sun.com/

Java is Portable

SYNTAX:

javac <filename>.java

EXAMPLE:

javac Welcome.java

You can compile your Java code from the command line.

Java is Portable

SYNTAX:

java <filename>

EXAMPLE:

java Welcome

Java program can then execute on any machine which has the Java Virtual Machine, thus, making it portable.

Java is Portable

Java Virtual Machine

Java code (*.java)

bytecodes (*.class)

Java Compiler

MAC PC UNIX

IDE: BlueJ

Download the appropriate version

Check the system requirements

Install J2SE 1.4.2 (Java 2 SDK version

1.4.2) or newer first before installing BlueJ

Download BlueJ: http://www.bluej.org/download/download.html

IDE: BlueJ

Minimum Requirements:

Pentium II processor or its

equivalent

64Mb main memory

Recommended:

400MHz Pentium III processor

or above and a 128Mb main

memory

Launch BlueJ

Let‟s make your

first Java project

using BlueJ…

Sample codes

package Group.Student;

public class Welcome{

public void printWelcome() {

System.out.println("Welcome to Java!"); //prints_a_msg

Sample codes

This class contains the main() method

public class Main {

public static void main(String args[]) {

Welcome Greet= new Welcome();

Greet.printWelcome();

Common Programming Errors

compile-time errors

runtime errors

Compile Time Error

Run-Time Error

Word Bank

object

interface

message

method

inheritance

encapsulation

compile-time errors

runtime errors

End of Lesson 1

Summary…

End of Lesson 2

Laboratory Exercise

Self-check

Create a class and describe it in terms of its attributes (data) and functions

(methods). Then, instantiate at least 2 objects. Use the tables below.

//write the class name here

Class Human

//write the data of the class here

Birthday

//write the methods of the class here

Give_Name

Get_Name

Get_Age

//write the object name here

//write the data of the object

Name: Jonathan

Age: 29

Birthday: March 4, 1975

//write the methods of the object

Give_Name

Get_Name

Get_Age

Self-check

Create a class and describe it in terms of its attributes (data) and functions

(methods). Then, instantiate at least 2 objects. Use the tables below.

//write the class name here

//write the data of the class

//write the methods of the

class here

//write the object name here

//write the data of the object

//write the methods of the

object here

Skills Workout

Type the Java program given in this

lesson in the specified package.

Compile and run it. If errors are

encountered, debug it.

Your First Java Program

Lesson 2

Welcome.java

public class Welcome{

public void printWelcome() {

System.out.println("Welcome to Java!"); //prints_a_msg

Explaining Welcome.java

Line 1 A single line comment.

A comment is read by he java compiler but, as a

command, it is actually ignored.

Any text followed two slash symbols(//) is

considered a comment.

Example:

// Welcome to Java

Line 2 defines the beginning of the Welcome

class. When you declare a class as public, it

can be accessed and used by the other class.

Notice that there is also an open brace to indicate

the start of the scope of the class.

To declare a class here is the syntax

<method>class<class_name>

Example: public class Welcome{

Void is the return type for the printWelcome()

Method. A method that returns void returns nothing. Return

type are discussed further in lesson 8

Example: public void printWelcome() {

Line 3 shows the start of the method printWelcome().

Syntax :

(<argument_list>) { <statements>) }

Example:

System.out.println("Welcome to Java!");

Line 4 shows how to print text in java. The

println() method displays the message inside the

parentheses on the screen, and then the cursor is

placed on the next line. If you want cursor to go to

the next available space after printing, use print()

method.

Syntax:

System.out.println(String);

Line 5 and 6 }

Contains closing braces. The braces on line 5 closes the method printWelcome() and the braces on line 6 closes the class Welcome.Take note that the opening brace on line 3 is paired with the closing brace on line 5 and the brace on line 2 is paired with the closing brace on line 6

Explaining Main.java

public class Main {

Greet.printWelcome();

Explaining Main.java Line 1-3

Contains a multi-line comment. Anyting in between /* and */ is considered a comment.

Explaining Main.java

Line 5

Declares the Main class. the brace after the class indicates the start of the class.

public class Main {

Explaining Main.java Line 6

Program execution starts from line 6. The Java interpreter should see this main method definition as

is, except for args which is user defined.

public class Main {

Explaining Main.java Line 7 shows how an object is defined in Java. Here, the

object Greet is created. The word “Greet” is user defined. (You can even have your name in its place!). The general syntax for defining an object in Java is:

Syntax:

<class_name> <object_name> = new<class_name>(<arguments>);

Example: Welcome Greet= new Welcome();

Explaining Main.java Line 8

Illustrates how a method of a class is called. If you look at the Welcome class, you’ll notice that we declared a mehod named printWelcome().By declaring an instance of the Welcome class (in tis case, the Greet variable is an instance of a Welcome class, courtesy of line 7), you can execute the method withi the specific class.

Syntax: <class_name>.<method_name>(<arguments>);

Example: Greet.printWelcome();

Explaining Main.java Line 9-10

Contains wo closing braces. The brace on line 9 closes the main method and brace on line 10 indicates the end of the scoope of the class Main.

Word Bank

new - used in telling the compiler to create

an object from the specified class.

public - modifier that indicates a class,

method, or class variable can be

accessed by any object or method directly.

End of Lesson 2

Summary…

Syntax Review SYNTAX EXAMPLE/S

package <top_package_name>[.<subpackage_name>]*;

import <top_package_name>[.<subpackage_name>]. <class_name>;

import School.Section.Student;

import School.Section.*;

<modifier> class <class_name> public class First

<class_name> <object_name> = new <class_name> (<arguments>);

< package_name>.<class_name> <object_name> = new <package_name>.<class_name>(<arguments>);

School.Section.Student Alma = new School.Section.Student ();

<modifier> <return_type> <method_name> (<argument_list>) { <statements>}

public static void main(String args[]) { }

public void printWelcome( ) { }

Syntax Review

SYNTAX EXAMPLE/S

System.out.println(String); System.out.println("Welcome to Java!");

System.out.print (String); System.out.print("Hello");

multi-line comment

//single line comment // author@

//prints_a_msg

Java doc multi-line comment

This method will compute the sum of two

integers and return the result.

Self-check

Below is a simple Java program that will print your name and age on the

screen. Fill the missing portions with the correct code. Type the program,

compile and run it.

2 This class contains the main() method

4 package Group.Student;

6 public class First {

7 public static void main(String args[]) {

8 Name ____________= new Name();

9 myName.________________();

First.java //filename

Self-check

Below is a simple Java program that will print your name and age on the

screen. Fill the missing portions with the correct code. Type the program,

compile and run it.

1 package Group.Student;

2 // author@

3 public class __________{

4 public void printName() {

5 System.out.print("____________");// prints your name

6 System.out.println("____________");//prints your age

Name.java //filename

End of Lesson 2

Laboratory Exercise

Data Types, Literals, Keywords and

Identifiers

Lesson 3

Magic words

Casting – process of converting a value to the

type of variable.

Constant – identifier whose value can never be

changed once initialized.

Identifier – user-defined name for methods,

classes, objects, variables and labels.

Literals – values assigned to variables or constant

Unicode – universal code that has a unique number to represent each character.

Variable – identifier whose value can be changed.

Java keyword – word used by the Java compiler for a specific purpose

Java Keywords

Some key points about Java keywords:

• const and goto are keywords but are

not used in Java.

• true and false are boolean literals that

should not be used as identifiers.

• null is also considered a literal but is

not allowed as an identifier.

Identifiers

Rules for Identifiers:

• The first character of your identifier can start with a

Unicode letter.

• It can be composed of alphanumeric characters and

underscores.

• there is no maximum length

• create identifiers that are descriptive of their purpose.

• Your identifier must have no embedded spaces.

• Special characters such as ? and like are not accepted.

Data Types

Java has two sets of data types:

• primitive

• reference (or non-primitive).

Data Types

Data Type Default

boolean false

char „\u0000‟

byte 0

short 0

long 0

float 0L

double 0.0D

Data Types

Data Type Examples

boolean true

char „A‟,‟z‟,‟\n‟,‟6‟

byte 1

short 11

int 167

long 11167

float 63.5F

double 63.5

Variables

Variable Declaration Syntax:

<data_type> <identifier>;

Examples: boolean Passed;

char EquivalentGrade’;

byte YearLevel;

short Classes;

int Faculty_No;

long Student_No;

float Average;

Variables and Literals

Variable and Literal Declaration Syntax: <data_type> <identifier>=<literal>;

Examples: boolean Passed=true;

char EquivalentGrade=’F’;

byte YearLevel=2;

short Classes=19;

int Faculty_No=6781;

long Student_No=76667;

float Average=76.87F;

Variables and Literals

Examples: boolean Passed =true, Switch;

char EquivalentGrade=’F’,ch1, ch2;

byte Bytes, YearLevel =2;

short SH, Classes =19;

int Faculty_No =6781, Num1;

long Student_No =76667, Employee_No, Long1;

float Average=96.89F, Salary;

double Logarithm=0.8795564564, Tax, SSS;

String LastName=”Your LastName”,FirstName=”Your FirstName”,

MiddleName;

You can also declare several variables for

a specific data type in one statement by

separating each identifier with a comma(,)

Constants

Syntax for declaring constants:

static final <type> <identifier> =

<literal>;

final <type> <identifier> = <literal>;

Example: static final String Student_ID=”098774656”;

Type Conversion/ Casting

Casting

• the process of assigning a value of a

specific type to a variable of another

• The general rule in type conversion is:

• upward casts are automatically done.

• downward casts should be expressed

explicitly.

Sample Code package Group.Lesson3;

public class Core

public Core(){ }

* The main method illustrates implicit casting from char to int

* and explicit casting.

public static void main(String[] args)

int x=10,Average=0;

byte Quiz_1=10,Quiz_2=9;

char c='a';

Average=(int) (Quiz_1+Quiz_2)/2; //explicit casting

x=c; //implicit casting from char to int

System.out.println("The Unicode equivalent of the character 'a' is : "+x);

System.out.println("This is the average of two quizzes : "+Average);

End of Lesson 3

Summary…

Self-check I. Write I if the given is not an acceptable Java identifier on the space provided

before each number. Otherwise, write V.

________________ 1.) Salary

________________ 2.) $dollar

________________ 3.) _main

________________ 4.) const

________________ 5.) previous year

________________ 6.) yahoo!

________________ 7.) else

________________ 8.) Float

________________ 9.) <date>

________________10.) 2_Version

II. Write C if the given statement is correct on the space provided before each

number. Otherwise, write I. Correct statements do not contain bugs.

________________1.) System.out.print(“Ingat ka!”, V);

________________2.) boolean B=1;

________________3.) double=5.67F;

________________4.) char c=(char) 56;

________________5.) System.out.print(„ I love you! „);

Self-check III.Below is a simple Java program that will print your name and age on the screen.

Fill the missing portions with the correct code. Type the program, compile and

run it.

public class First

public ________________(){ }//Constructor for objects of class Core

int I=90;

short S=4;

________________;//statement to cast I to S

System.out.println(“I=___________________ );//print I

System.out.println(“S=___________________ );//print S

End of Lesson 10

LABORATORY EXERCISE

Java Operators

Lesson 4

Operators

• Unary

• Binary

• Ternary

• Shorthand

Arithmetic Operator

Operators

+ Addition

- Subtraction

* Multiplication

/ Division

% Modulo

++ Increment

-- Decrement

The Arithmetic_operators program package Group.Lesson4.Arithmetic;

public class Arithmetic_operators

public Arithmetic_operators() { } // Constructor

int x=30, y= 2;

int Add=0,Subtract=0,Multiply=0,Divide=0;

int Modulo=0,Inc1=0,Inc2=0,Dec1=0,Dec2=0;

Add=x+y;

Subtract=x-y;

Multiply=x*y;

Divide=(int)x/y;

Modulo=x%y;

The Arithmetic_operators program (Continued) System.out.println("30+2="+Add+"\n30-2="+Subtract);

System.out.println("30*2="+Multiply+"\n30/2="+Divide+"\n30%2="+Modulo);

System.out.println("x="+x+"\ny="+y);

Inc1=x++;

Inc2=++y;

System.out.println("Inc1="+Inc1+"\nInc2="+Inc2);

Dec1=--x;

Dec2=y--;

System.out.println("Inc1="+Inc1+"\nInc2="+Inc2);

The Arithmetic_operators program output

Relational Operator

> Greater than

>= Greater than or equal to

< Less than

<= Less than or equal to

= = Equal to

!= Not Equal to

The Relational_operators program

package Group.Lesson4.Relational;

public class Relational_operators

public Relational_operators() { }// Constructor for objects of class

Relational_operators

public static void main(String[] args)//execution begins here

//local variables

int x = 5, y = 7;

boolean Relational_Equal=false, Relational_NotEqual=false;

boolean Relational_LessThan=false, Relational_LessThanOrEqualTo=false;

boolean Relational_GreaterThan=false;

boolean Relational_GreaterThanOrEqualTo=false;

//evaluate expressions

Relational_Equal= x==y;

Relational_NotEqual= x!=y;

Relational_LessThan= x<y;

Relational_LessThanOrEqualTo= x<=y;

Relational_GreaterThan= x>y;

Relational_GreaterThanOrEqualTo= x>=y;

//print results

System.out.println("x=5 y=7");

System.out.println("x==y "+Relational_Equal);

System.out.println("x!=y "+Relational_NotEqual);

System.out.println("x<y "+Relational_LessThan);

System.out.println("x<=y

"+Relational_LessThanOrEqualTo);

System.out.println("x>y "+Relational_GreaterThan);

System.out.println("x>=y

"+Relational_GreaterThanOrEqualTo);

The Relational_operators program (Continued)

The Relational_operators program output

Logical Operator

Operators Description

&& AND

| short-circuit OR

& short-circuit AND

Logical Operator- Truth Tables

Operand1 RESULT

! true false

! false true

The NOT (!) operator

The OR (|) operator

Operand1 Operand2 RESULT

true | true true

true | false true

false | true true

false | false false

The XOR (^) operator

true ^ true false

true ^ false true

false ^ true true

false ^ false false

The AND (&) operator

true & true true

true & false false

false & true false

false & false false

The Logical_operators program package Group.Lesson4.Logical;

public class Logical_operators

// Constructor for objects of class Logical_operators

public Logical_operators(){}

//local variables

int x = 6 , y = 7;

boolean Logical_OR=false, Logical_OR_ShortCircuit=false;

boolean Logical_AND=false, Logical_AND_ShortCircuit=false;

boolean Logical_NOT=false, Logical_XOR=false;

System.out.println("x=6 y=7");

Logical_OR_ShortCircuit= (x<y)| (x++==y);

System.out.println("(x<y)| (x++==y) "+Logical_OR_ShortCircuit);

Logical_OR= (x<y)||(x++==y);

System.out.println("(x<y)| (x++==y) "+Logical_OR);

Logical_AND_ShortCircuit=(x<y)& (x==y++);

System.out.println("(x>y)& (x++==y) “ +Logical_AND_ShortCircuit);

Logical_AND= (x<y)&&(x++==y);

System.out.println("(x>y)&&(x++==y) "+Logical_AND);

Logical_NOT= !(x>y)||(x++==y);

System.out.println("!(x>y)||(x++==y) "+Logical_NOT);

Logical_XOR= (x>y)^ (x++==y);

System.out.println("(x>y)^ (x++==y) "+Logical_XOR);

System.out.println("!((x>y)^ (x++==y)) "+!Logical_XOR);//NEGATE

The Logical_operators program (Continued)

The Logical_operators program output

REVIEW

Try converting 16 and 27 to bits.

Hope you got these answers: 16=0000000000010000

27=0000000000011011

RECALL: How do you get the equivalent of a certain number in bits?

ANSWER: You divide the number by 2 until you reach 0. Jot down the

remainder for each division operation and that‟s the equivalent.

RECALL: How do you convert a bit sequence to integer?

ANSWER: You multiply each bit by powers of 2. Then, add all the

products to get the equivalent.

RECALL: How many bits does an integer have?

ANSWER: 16 bits

REVIEW

Example: 4=0000000000000100

-4=1111111111111100

If you have a negative number, you still

have to convert the same way you would if it

were a positive number. Then, get the

complement and add 1. That‟s it!

Bitwise Operator

~ Complement

^ XOR (Exclusive OR)

<< Left Shift

>> Right Shift

>>> Unsigned Right Shift

Bitwise Operator - Truth Tables

The BITWISE COMPLEMENT

Operand1 RESULT

The BITWISE OR (|)

1 | 1 1

1 | 0 1

0 | 1 1

0 | 0 0

The BITWISE XOR (^)

1 ^ 1 0

1 ^ 0 1

0 ^ 1 1

0 ^ 0 0

The BITWISE AND (&)

1 & 1 1

1 & 0 0

0 & 1 0

0 & 0 0

Bitwise Operator – Examples

x= 0000000000010000

~x= 1111111111101111

Therefore, ~x=-17.

x= 0000000000010000

y= 0000000000011011

Or= 0000000000011011

x= 0000000000010000

y= 0000000000011011

And= 0000000000010000

x= 0000000000010000

y= 0000000000011011

Xor= 0000000000001011

x= 0000000000010000

Left_shift=

0000000010000000

Left_shift = 128

z= 1111111111111100

Right_shift= 1111111111111111

Right_shift= -1

Negative=1111111111111100

Negative=0011111111111111

Negative= 1073741823

The Bitwise_operators program package Group.Lesson4.Bitwise;

public class Bitwise_operators

//Constructor for objects of class Bitwise_operators

public Bitwise_operators() { }

//local variables

int x = 16 , y = 27, z=-4, Negative=-4;

int Complement=0,Or=0,And=0,Xor=0,Left_shift=0;

int Right_shift=0, Unsigned_Right_shift=0;

//operations

Complement = ~x;

Or = x|y;

And = x&y;

Xor = x^y;

Left_shift = x<<3;

Right_shift = z>>2;

Unsigned_Right_shift= Negative>>>2;

//print results

System.out.println("x=16 y=7 z=-4");

System.out.println("~x = "+Complement);

System.out.println("x|y = "+Or);

System.out.println("x&y = "+And);

System.out.println("x^y = "+Xor);

System.out.println("x<<3 = "+Left_shift);

System.out.println("z>>2 = "+Right_shift);

System.out.println("Negative>>>2 = "+Unsigned_Right_shift);

The Bitwise_operators program (continued)

The Bitwise_operators program output

Shorthand Operator with Assignment

+= Assignment With Addition

-= Assignment With Subtraction

*= Assignment With Multiplication

/= Assignment With Division

%= Assignment With Modulo

&= Assignment With Bitwise And

|= Assignment With Bitwise Or

^= Assignment With Bitwise XOR

<<= Assignment With Left Shift

>>= Assignment With Right Shift

>>>= Assignment With Unsigned Right

The Shorthand_operators program

package Group.Lesson4.Shorthand;

public class Shorthand_operators

{ //Constructor for objects of class Shorthand_operators

public Shorthand_operators(){ }

{ //local variables

int Assign_With_Addition=4, Assign_With_Subtraction=4, Assign_With_Multiplication=4;

double Assign_With_Division=7;

int Assign_With_Modulo=7, Assign_With_Bitwise_And=7;

int Assign_With_Bitwise_Or=23, Assign_With_Bitwise_XOR=23, Assign_With_LeftShift=23;

int Assign_With_RightShift=10, Assign_With_UnsignedRightShift=10;

Assign_With_Addition +=2;

Assign_With_Subtraction -=2;

Assign_With_Multiplication *=2;

Assign_With_Division /=2;

Assign_With_Modulo %=2;

Assign_With_Bitwise_And &=2;

Assign_With_Bitwise_Or |=2;

Assign_With_Bitwise_XOR ^=2;

Assign_With_LeftShift <<=2;

Assign_With_RightShift >>=2;

Assign_With_UnsignedRightShift >>>=2;

System.out.println(" Results");

System.out.println("Assign_With_Addition+=2 "+Assign_With_Addition);

System.out.println("Assign_With_Subtraction-=2 "+Assign_With_Subtraction);

System.out.println("Assign_With_Multiplication*=2 "+Assign_With_Multiplication);

System.out.println("Assign_With_Division/=2 "+Assign_With_Division);

System.out.println("Assign_With_Modulo%=2 "+Assign_With_Modulo );

System.out.println("Assign_With_Bitwise_And&=2 "+Assign_With_Bitwise_And);

System.out.println("Assign_With_Bitwise_Or|=2 "+Assign_With_Bitwise_Or );

System.out.println("Assign_With_Bitwise_XOR^=2 "+Assign_With_Bitwise_XOR);

System.out.println("Assign_With_LeftShift<<=2 "+Assign_With_LeftShift);

System.out.println("Assign_With_RightShift>>=2 "+Assign_With_RightShift);

System.out.println("Assign_With_UnsignedRightShift>>>=2 "+Assign_With_UnsignedRightShift);

The Shorthand_operators program (continued)

The Shorthand_operators program output

Operator Precedence

Word Bank

expression

boolean expressions

truth value

truth table

shorthand operators

sign bit

End of Lesson 4

Summary…

Self-check

Evaluate the given expressions/statements. Write

the result on the blanks provided before each

number. Given that a=3, b=4,c=6.

1.x=a++;

2.y=--b;

3.!((++a)!=4)&&(--b==4))

4.(c++!=b)|(a++==b)

5.t=a+b*c/3-2;

Decisions

Lesson 5

Decision making

In life we make decisions. Many times our decision are based on how we evaluate the situation. Certain situation need to be evaluated carefully in order to make the correct results or decision.

In Java , decisions are made using statements like if, if else, nested-if and switch.

In this lesson , we will examine hot these conditional statements are applied to simple programming problems.

Decision Statements If Statement: public class If_Statement

public static void main (String [] args)

int x = 0;

System.out.println ("Value is:" + x);

if(x%2==0)

System.out.println ("VAlue is an even number.");

if (x%2 ==1)

System.out.println ("Value is an odd number.");

Wrapper Class

Primitive Data

Wrapper Class

boolean Boolean

char Character

byte Byte

short Short

int Integer

long Long

float Float

double Double

if Statement

Syntax:

if (<boolean condition is true>)

Example: if(x!=0){

x=(int)x/2;

The If_Statement program

package Lesson5.If;

import java.io.*;

public class If_Statement

//Constructor for objects of class If_Statement

public If_Statement(){ }

public static void main(String[] args) throws IOException

BufferedReader dataIn=new BufferedReader(new InputStreamReader(System.in));

int x=0;

String Str_1;

System.out.print("Enter an integer value: ");

Str_1=dataIn.readLine();

x=Integer.parseInt(Str_1);

if(x!=0){

x=(int)x/2;

System.out.println("x= "+x);

if-else Statement

Example: if (A%2==0) {

System.out.println (A+" is an EVEN number");

} else {

System.out.println (A+" is an ODD number");

Syntax:

if (<boolean condition is true>){

package Lesson5.If_Else;

import java.io.*;

public class IfElse {

public IfElse() { }

public static void main(String[] args)throws IOException

//declare local variables

int A=0;

String Str_A;

//input

System.out.print("Enter an integer value for A: ");

Str_A=dataIn.readLine();

A=Integer.parseInt(Str_A);

//determine if input is odd or even and print

if (A%2==0) {

System.out.println (A+" is an EVEN number");

} else {

System.out.println (A+" is an ODD number");

The IfElse program

nested-if Statement

Syntax: if (<boolean condition is true>){

else if (<boolean condition is true>) {

Example:

if (number1>number2) {

System.out.println (number1+" is greater than "+number2);

} else if (number1<number2){

System.out.println (number1+" is less than "+number2);

} else {//number1==number2

System.out.println (number1+" is equal to "+number2);

nested-if Statement

public class NestedIf {

public NestedIf() { }

public static void main(String[] args)throws IOException

//declare local variables

double number1=0.0,number2=0.0;

String Str_number1,Str_number2;

//input Str_number1 and convert it to an integer (number1)

System.out.print("Enter a number: ");

Str_number1=dataIn.readLine();

number1=Double.parseDouble(Str_number1);

//input Str_number2 and convert it to an integer (number2)

System.out.print("Enter another number: ");

Str_number2=dataIn.readLine();

number2=Double.parseDouble(Str_number2);

//determine if number1 is greater than, less than or equal to number2

The NestedIf program and output

switch Statement

Syntax: switch(<expression>) {

case <constant1>:

break;

case <constant2>:

break;

default:

break;

Example:

switch(month){

case 1:System.out.println("January has 31 days");

break;

case 2:System.out.println("February has 28 or 29 days");

break;

case 3:System.out.println("March has 31 days");

default:System.out.println("Sorry that is not a valid month!");

break;

switch Statement

public Switch_case(){ }//Constructor for objects of class Switch_case

public static void main(String[] args) throws IOException{

BufferedReader dataIn=new BufferedReader(new

InputStreamReader(System.in));

int month=0;

String Str_month;

System.out.print("Enter month [1-12]: ");

Str_month=dataIn.readLine();

month=Integer.parseInt(Str_month);

switch(month){

case 1:System.out.println("January has 31 days");

break;

case 2:System.out.println("February has 28 or 29 days");

break;

case 3:System.out.println("March has 31 days");

break;

case 4:System.out.println("April has 30 days");

break;

case 5:System.out.println("May has 31 days");

break;

The Switch_case program

case 6:System.out.println("June has 30 days");

break;

case 7:System.out.println("July has 31 days");

break;

case 8:System.out.println("August has 31 days");

break;

case 9:System.out.println("September has 30 days");

break;

case 10:System.out.println("October has 31 days");

break;

case 11:System.out.println("November has 30 days");

break;

case 12:System.out.println("December has 31 days");

break;

default:System.out.println("Sorry that is not a valid month!");

break; }}}

The Switch_case program (continued) and output

Word Bank

Wrapper class

End of Lesson 5

Summary…

End of Lesson 10

LABORATORY EXERCISE

Syntax Review

SYNTAX EXAMPLE/S

if (<boolean condition is

true>) {

if(x!=0){

x=(int)x/2;

if (<boolean condition is

true>){

if (A%2==0) {

System.out.println (A+" is EVEN");

System.out.println (A+" is ODD ");

Syntax Review SYNTAX EXAMPLE/S

if (<boolean condition is true>){

else if (<boolean condition is true>) {

switch(<expression>) {

break;

break;

default:

break;

switch(Number){

case 1:System.out.println("One ");

break;

case 2:System.out.println("Two");

break;

case 3:System.out.println("Three");

break;

default:System.out.println("Sorry!");

break;

Self-check

In the next slide is a simple Java program

that will determine if a number is zero, positive or

negative then print the appropriate message on

the screen. Fill the missing portions with the

correct code. Type the program, then compile and

run it.

Self-check public class NestedIf {

public NestedIf() { }//constructor

int number=3;

if (__________) // FILL-IN THE BLANK

System.out.println (number+” is ZERO!”);

else if (___________) //FILL-IN THE BLANK

System.out.println (number+" is a POSITIVE number!”);

System.out.println (number+" is a NEGATIVE number!”);

Lesson 6

General Topics

• for structure

• while structure

• do-while structure

A loop is a structure in Java that

permits a set of instructions to

be repeated

The for loop is usually used when the number of iterations that needs to be done is already known.

The while loop checks whether the prerequisite condition to execute the code within the loop is true or not. If it is true, then the code loop is executed.

The do-while loop executes the code within it first regardless of whether the condition is true or not before testing the given condition.

3 Main Parts of for loop Initialization - initial values of variables

that will be used in the loop.

Test condition - a boolean expression that

should be satisfied for the loop to

continue executing the statements

within the loop’s scope; as long as the

condition is true.

Increment/Operations- dictates the change

in value of the loop control variable

everytime the loop is repeated.

for loop

Syntax: for (<initialization>;<condition>;<increment>)

Example:

for(int Ctr=1;Ctr<=5;Ctr++){

System.out.println(Ctr);

The For_loop program and output

package Lesson6.For;

public class For_loop

public For_loop() { }

for(int Ctr=1;Ctr<=5;Ctr++){

while loop

Syntax: while (boolean condition is true)

Example:

int Ctr=1;

while(Ctr<=5){

Ctr++;

Sample Code and output

public class While_Loop

//Constructor for objects of class While_loop

public While_Loop() { }

int Ctr=1;

while(Ctr<=5){

Ctr++;

do-while loop

Syntax: do {

} while (<boolean condition is true>);

Example:

int Ctr=1;

Ctr++;

}while(Ctr<=5);

Sample Code

public class DoWhile

public DoWhile() { }

int Ctr=1;

Ctr++;

}while(Ctr<=5);

End of Lesson 6

Summary…

Self-check

In the next slides are three

simple Java programs. Fill

the missing portions with

the correct code. Type the

programs, compile and run

Self-check (For_loop2)

public class For_loop2

//Constructor for objects of class For_loop2

public For_loop2() { }

* main()-prints all even numbers from 1-10

automatically using a for loop

* @param String[] args

* @return nothing

for(int Ctr=____;Ctr<=_____;Ctr____){

Self-check (DoWhile2)

public class DoWhile2

//Constructor for objects of class DoWhile2

public DoWhile2() { }

* main()-prints the numbers 1-10 automatically

using a do_while loop

* @return nothing

int Ctr=________;

Ctr______;

}while(Ctr<=_________);

Self-check (While_Loop2)

public class While_Loop2

//Constructor for objects of class While_loop2

public While_Loop2() { }

* main()-prints odd numbers from 2 to 20

automatically using a while loop

* @return nothing

int Ctr=____________;

while(Ctr<=__________){

Ctr_______________;

End of Lesson

LABORATORY EXERCISE

More Loops

General Topics

• Nested loops

• continue

• break

Nested_For loops

The Nested_For program prints the multiplication

table. To do this, it has two loops. One loop is

inside the other. This is why it is called a nested

Nested_For loops

public class Nested_For

// Constructor for objects of class Nested_For

public Nested_For(){ }

public static void main(String [] args)

for(int Row=1;Row<=10;Row++){

for(int Column=1;Column<=10;Column++){

System.out.print(Row*Column+"\t");

System.out.println();

To see how this program behaves at any given time,

we need to set breakpoints. To do that, just click on

line number.

Nested_For loops – how it behaves

Click on line 15.

Run the program by right-clicking on the Nested_For

icon, click on void main(String [] args).

Then, click on the

Ok button.

– how it behaves

Nested_For loops – Output

The difference is the

inclusion of the if

statement on line 17

and the continue

statement on line 18.

Continue_Loop

public class Continue_Loop

// Constructor for objects of class Continue_Loop

public Continue_Loop(){ }

if(Column==4){

continue;

Continue_Loop - Output

The column containing the multiples of 4 is not included.

Loop_Break

This program is again

similar to the previous

programs in this lesson,

except for the inclusion

of the if and break

statements. The output

shows 3 columns only.

Loop_Break

public class Loop_Break

//Constructor for objects of class Loop_Break

public Loop_Break(){ }

if(Column==4){

break;

Labels

public class Labels

//Constructor for objects of class Labels

public Labels() { }

here: for(int Row=1;Row<=10;Row++){

if(Column==4){

break here;

Word Bank

Nested loops

Self-check

I. A Java program that prints the multiplication table is given using nested

while loops. Fill-in the missing portions.

public class Multiplication_Table

// Constructor for objects of class Multiplication_Table

public Multiplication_Table (){ }

int Row=_______; //indicate the initial value

while(Row<____){

Row++;

int Column=_____; //indicate the initial

while(Column<_____){

Column++;

Self-check

II. A Java program that prints the given output using nested do-while loops.

Fill-in the missing portions.

Self-check

public class Table{

// Constructor for objects of class Table

public Table(){ }

public static void main(String [] args) {

int Row=_______; //indicate the initial value

Row++;

int Column=_____; //indicate the

initial value

Column++;

if(_______){

continue;

} while(Column<_____);

} while(Row<____);

LESSON 7

Exceptions

Unexpected errors or events within our program

import java.io.*; public class Exception1{ public static void main(String[] args){ BufferedReader dataIn = new BufferedReader(new InputStreamReader(System.in));

int x=0; String Str_1; System.out.print(“Enter an integer value:”); try{ Str_1 = dataIn.readLine(); x = Integer.parseInt(Str_1); } catch(Exception e){ System.out.println(“Error reported”); } x = (int)x/2; System.out.println(“x= ”+x); } }

import java.io.*; public class Exception2{

public static void main(String[] args){ BufferedReader dataIn = new BufferedReader(new InputStreamReader(System.in));

int x=0, y=0; String Str_1, Str_2;

System.out.print(“Enter an integer value: ”); try{

Str_1 = dataIn.readLine();

System.out.print(“Enter another value: ”); Str_2 = dataIn.readLine();

x = Integer.parseInt(Str_1); y = Integer.parseInt(Str_2);

x = x/y; }

catch(ArithmeticException e){

System.out.println(“Divide by zero error.”);

catch(NumberFormatException e){

System.out.println(“Invalid number entered.”);

catch(Exception e){

System.out.println(“Invalid number entered.”);

finally{

System.out.println(“x= ”+x);

Exceptions

Exception classes

finally

Exception classes

Help handle errors

Included within Java installation package

try-catch

At least one catch for every try

catch statements should catch different exceptions

try-catch order

catch immediately after a try

End of Lesson

LABORATORY EXERCISE

Classes

Lesson 8

General Topics

• Classes

• Inheritance

• Interface

• Objects

• Constructors

• Overloading Methods

• Overriding Methods

Classes

Accessibility

Syntax

<modifier> class <class_name>

[extends <superclass>] {

Example:

public class Student extends Person

Syntax

<modifier> class <name>

[extends <superclass>]

[implements <interfaces>] {

Example:

public class Teacher

extends Person

implements Employee

Syntax

<modifiers> class

<class_name>{

[<attribute_declarations>]

[<constructor_declarations>]

[<method_declarations>]

The Person program

package Lesson8;

public class Person extends Object

private String name;

private int age;

private Date birthday;

// class constructor

public Person() {

name = "secret";

age = 0;

birthday = new Date(7,7);

//overloaded constructor

public Person(String name, int age, Date birthday){

this.name = name;

this.age = age;

this.birthday = birthday;

The Person program (continued) //accessor methods - setters

public void setName(String X){

name= X;

public void setAge(int X) {

age=X;

public void setBirthday(Date X){

birthday=X;

public void setDetails(String X, int Y, Date Z){

name= X;

age=Y;

birthday = Z;

//accessor methods - getters

public String getName(){

return name;

The Person program (continued)

public int getAge(){

return age;

//this method greets you on your bday and increments age

public void happyBirthday(Date date){

System.out.println("Today is

"+date.month+"/"+date.month+"/2005.");

if (birthday.day == date.day && birthday.month == date.month){

System.out.println("Happy birthday, "+ this.name + ".");

age++;

System.out.println("You are now "+age+" years old.");

else {

System.out.println( "It's not " + this.name + "'s birthday today.");

The Someone program package Lesson8;

public class Someone

public static void main (String args[]){

Date dateToday = new Date(3,7);

Date bdayLesley= new Date(23,10);

Person Angelina=new Person();

Student Stevenson = new Student("Stevenson",20,new Date(22,10),4);

Student Allan =new Student(3);

Teacher Lesley= new Teacher("Lesley",28,bdayLesley,14000.25);

Angelina.setName("Angel");

Angelina.setAge(69);

Angelina.setBirthday(dateToday);

System.out.println("Greetings, "+Angelina.getName());

Angelina.happyBirthday(dateToday);

Allan.setDetails("Allan",20,new Date(3,5));

The Date program

package Lesson8;

public class Date

{ // instance variables - replace the example below with your own

int day, month, year;

//Constructor for objects of class Date with no parameters

public Date()

{ // initialize instance variables

day = 1;

month=1;

year=2005;

The Date program (continued) //Constructor for objects of class Date with day & month as parameters

public Date(int this_Day,int this_Month)

{ // initialise instance variables

if((this_Month>=1)&&(this_Month<=12)){

month=this_Month;

switch(month){

case 1: case 3: case 5: case 7: case 8: case 10:

case 12:if((this_Day>=1)&&(this_Day<=31)){day = this_Day;}

else {day=1;}

break;

case 4: case 6: case 9:

case 11:if((this_Day>=1)&&(this_Day<=30)){ day = this_Day;}

else {day=1;}

break;

else {day=1;}

break;

} else { month=1; }

year=2005; }

The Date program (continued)

public void print_Date(){//prints the date mm/dd/yyyy

System.out.println(month+"/"+day+"/"+year); }

The Student program package Lesson8;

public class Student extends Person

private int yearlvl;

//constructors

public Student(){

super();

yearlvl=1;

public Student(int yearlvl) {

super();

if((yearlvl<=4)&&(yearlvl>=1)){

this.yearlvl=yearlvl;

} else {

this.yearlvl=1;

The Student program (continued)

public Student(String name, int age, Date birthday, int

yearlvl){

super(name, age, birthday);

} else {

this.yearlvl=1;

System.out.print("Hi, "+name+". ");

System.out.print(“Your birthday this year is on ");

birthday.print_Date();

System.out.println("You are "+age+" years old.");

//accessor methods

public void setYearlvl(int yearlvl){

} else {

this.yearlvl=1;

public void setDetails(String name, int age, Date birthday){

super.setDetails(name,age,birthday);

System.out.print("Hello, "+name+". ");

System.out.print("Your birthday this year is on ");

public void setDetails(String name, int age, Date birthday, int

yearlvl){

super.setDetails(name,age,birthday);

} else {

this.yearlvl=1;

System.out.print("Hello, "+name+". ");

System.out.print(" Your birthday this year is on ");

public int getYearlvl(){

return yearlvl;

The Teacher program

package Lesson8;

public class Teacher extends Person implements Employee

private double salary;

// constructors

public Teacher(){

super();

salary = 4000;

public Teacher(double salary) {

super();

this.salary = salary;

The Teacher program (continued)

public Teacher(String name, int age, Date birthday, double salary){

super(name, age, birthday);

this.salary= salary;

System.out.println("Good morning, "+name+". Your salary is "+salary+".");

System.out.println(" Your birthday this year is on ");

//accessor methods

public void setSalary(double salary) {

The Teacher program (continued)

public void setDetails(String name, int age, Date birthday, double salary){

super.setDetails(name, age, birthday);

System.out.println("Good afternoon, "+name+". Your salary is "+salary+".");

System.out.println(" Your birthday this year is on ");

System.out.println("You are now "+age+" years old.");

public double getSalary(){

return salary;

The Employee program

package Lesson8;

public interface Employee

public void setSalary(double salary);

public void setDetails(String name, int age, Date birthday, double salary);

public double getSalary();

Word Bank

Superclass

Subclass

Inheritance

Interface

Method

Signature

Overloading Constructor

Overriding Method

End of Lesson 8

SUMMARY

Syntax Review

The constructor of the superclass that has no parameters can be called this way:

super ( );

The constructor of the superclass that has parameters can be called this way:

super (<argument list> );

The syntax to call a method of the superclass is:

super.<method_name> (<argument list> );

Syntax Review

SYNTAX EXAMPLE/S

<modifier> class <class_name>

public class Student

extends Person

<modifier> class <name>

[implements <interfaces>]

public class Teacher

extends Person

implements Employee

Syntax Review (continued)

SYNTAX EXAMPLE/S

<modifiers> class <class_name>{

[<attribute_declarations>]

[<constructor_declarations>]

[<method_declarations>]

public class Person extends Object{

//attribute declarations

private String name;

private int age;

private Date birthday;

// class constructor

public Person() {

name = "secret";

age = 0;

birthday = new Date(7,7);

//accessor methods - setters

public void setName(String X){

name= X;

Self-check 1

A. Supply all the method signatures of Student to the

interface Learner, except for the constructors.

public interface Learner{

B. Create a constructor for Person with name and

age as parameters. Make sure that you assign

values to all the attributes of the class Person.

I. Use the applications given on our lesson for exercise A and B.

Self-check 2

II. Use this diagram in answering the next exercises.

Self-check

public interface FlyingObject{

A. Supply all the method signatures

of Plane to the interface

FlyingObject, except for the

constructors.

End of Lesson

LABORATORY EXERCISE

Arrays

Lesson 9

General Topics

• Single-dimensional arrays

• Array of Objects

• Multidimensional arrays

The Single_Array program

public class Single_Array

//Constructor for objects of class Single_Array

public Single_Array() { }

public static void main(String[] args){

int [] GradeLevel=new int [6];

int [] YearLevel={1,2,3,4};

System.out.print("The contents of the YearLevel array: ");

print_Single_Array(YearLevel);

System.out.print("The contents of the GradeLevel array: ");

print_Single_Array(GradeLevel);

System.arraycopy(YearLevel,0,GradeLevel,1,YearLevel.length);

System.out.print("The contents of the GradeLevel array after

copying: ");

for(int Index=1;Index<GradeLevel.length;Index++){

GradeLevel[Index]=Index*2;

System.out.print("The contents of the GradeLevel array after

assigning values: ");

public static void print_Single_Array(int[] Array){

for(int subscript=0;subscript<Array.length;subscript++){

System.out.print(Array[subscript]); //prints the array

element

if((subscript+1)<Array.length){ //prints a comma in-

between elements

System.out.print(", ");

The Single_Array program (continued) and output

Single Dimensional Array

SYNTAX:

<data_type> [ ] <array_identifier> = new <data_type>[<no_of_elements>];

<data_type> <array_identifier> [ ] = new <data_type>[<no_of_elements>];

[0] [1] [2] [3]

YearLevel 1 2 3 4

First Element Last Element

Example:

System.arraycopy

SYNTAX:

System.arraycopy(<Array_source>,

<Array_sourcePosition>,

<Array_destination>,

<Array_destinationPosition>,

<numberOfElements>);

The Date program

package Group.Lesson9.Array_Object;

* @author Lesley Abe

* @version 1

public class Date

{ // instance variables - replace the example below with your own

private int day, month, year;

//Constructor for objects of class Date with no parameters

public Date()

{ // initialize instance variables

day = 1;

month=1;

year=2005;

//Constructor for objects of class Date with day & month as parameters

The Date program (continued) public Date(int this_Day,int this_Month)

{ // initialise instance variables

if((this_Month>=1)&&(this_Month<=12)){

month=this_Month;

switch(month){

case 1: case 3: case 5: case 7: case 8: case 10:

else {day=1;}

break;

case 4: case 6: case 9:

case 11:if((this_Day>=1)&&(this_Day<=30)){ day = this_Day;}

else {day=1;}

break;

else {day=1;}

break;

} else { month=1; }

year=2005;

The Date program (continued)

Date[] Birthdays={ new Date(23,10), new Date(22,3) };

Date[] Holidays=new Date[4];

Holidays[0]=new Date(25,12);

The Two_Dimensional_Array program

public class Two_Dimensional_Array

{ //Constructor for objects of class Two_Dimensional_Array

public Two_Dimensional_Array() { }

final int YearLevel=4; // this is a constant

final int Section=2; //this is a constant

String TeacherName [] [] = new String [YearLevel] [Section];

String Student [] [] = new String [YearLevel] [ ]; //non-rectangular array

//String Student [] [] = new String [] [YearLevel]; //this is illegal!

//assign teachers to all the classes in high school

TeacherName [0] [0] = "Lesley Abe";

TeacherName [0] [1] = "Arturo Jacinto Jr.";

TeacherName [1] [0] = "Olive Hernandez";

TeacherName [1] [1] = "Alvin Ramirez";

TeacherName [2] [0] = "Christopher Ramos";

TeacherName [2] [1] = "Gabriela Alejandra Dans-Lee";

TeacherName [3] [0] = "Joyce Cayamanda";

TeacherName [3] [1] = "Ana Lisa Galinato";

The Two_Dimensional_Array program (continued)

//indicate how many student assistants per year level

Student [0]=new String [2];

//assign student assistants per year level

Student [0] [0]= "Stevenson Lee";

Student [0] [1]= "Brian Loya";

Student [1] [0]= "Joselino Luna";

Student [1] [1]= "Allan Valdez";

Student [2] [0]= "John Dionisio";

Student [3] [0]= "Geoffrey Chua";

The Two_Dimensional_Array program (continued)

Date[] Birthdays={ new Date(23,10), new

Date(22,3) };

Date[] Holidays=new Date[4];

Multi-Dimensional Array

SYNTAX:

<data_type> [ ][ ] <array_identifier> =

new <data_type>[<size1>][<size2>];

<data_type> <array_identifier> [ ] [ ]

<data_type>[<size1>][<size2>];

Word Bank

End of Lesson 9

SUMMARY

Syntax Review

SYNTAX EXAMPLE/S

<data_type> [ ] <array_identifier> = new <data_type>[<no_of_elements>];

int [ ] GradeLevel=new int [6];

<data_type> < array_identifier> [ ] = new <data_type>[<no_of_elements>];

int GradeLevel [ ] =new int [6];

<data_type> [ ] < array_identifier> = {< elements separated by commas>};

int [ ] YearLevel={1,2,3,4};

< array_identifier> [<Index>] = <value>; GradeLevel[Index]=Index*2;

<data_type> [ ][ ] <array_identifier> = new <data_type>[<size1>][<size2>];

String [ ] [ ] TeacherName = new String [YearLevel] [ ];

<data_type> <array_identifier> [ ] [ ] = new <data_type>[<size1>][<size2>];

String TeacherName [ ] [ ] = new String [YearLevel] [Section];

< array_identifier> [<Index1>] [<Index2>] = <value>;

TeacherName [0] [0] = "Lesley Abe";

System.arraycopy(<Array_source>, <Array_sourcePosition>, <Array_destination>, <Array_destinationPosition>, <numberOfElements>);

System.arraycopy(YearLevel,0,GradeLevel,1,YearLevel.length);

Self-check 1

public class Array1

//Constructor for objects of class Array1

public Array1() { }

public static void main(String[] args){

String [] __________={“Math”,”Science”,_________ };

String [] MyTeachers={______________ };

System.out.print("Here are my subjects: ");

print_Array1(MySubjects);

System.out.print("My favorite subject is: "+________);

System.out.print("My favorite teacher is: "+________);

//method that prints the contents of an array of String

public static void __________(_______[] Array){

for(intsubscript=0;subscript<Array.length;subscript++){

//prints the array element

System.out.print(__________); if(____________________){

//prints a comma in-between elements

System.out.print(", ");

Self-check 2

public class Array2

// Constructor for objects of class Array2

public Array2 (){ }

final int Row=5;

final int Column=5;

int [] [] Table=new int [Row][Column];

for(int Row_Ctr=0;Row_Ctr<Row;Row_Ctr++){

for(int Col_Ctr=0;Col_Ctr<Column;Col_Ctr++){

Table[Row_Ctr][Col_Ctr]= Row_Ctr+Col_Ctr;

Self-check 2 (continued)

What are the values of the following:

Table[0][0]= ___________

Table[2][1]= ___________

Table[1][3]= ___________

Table[4][4]= ___________

Table[3][2]= ___________

End of Lesson

LABORATORY EXERCISE

Lesson 10

General Topics

• Abstract Window Toolkit (AWT)

- java.awt package

- components

• Containers

• Layout Managers

Layout

SYNTAX:

FlowLayout( )

FlowLayout(int align)

FlowLayout(int align, int hgap, int

Examples:

setLayout(FlowLayout());

setLayout(FlowLayout(FlowLayout.LEF

setLayout(FlowLayout(FlowLayout.RIG

HT,23,10));

Layout

SYNTAX:

GridLayout( );

GridLayout(int rows, int cols);

GridLayout(int rows, int cols, int hgap, int vgap);

Examples:

setLayout(GridLayout());

SouthPanel.setLayout(new GridLayout(4,3));

Layout

SYNTAX:

BorderLayout( );

Examples:

setLayout(new BorderLayout());

Sample GUI Project

Project Output

The DrawTest program package Group.Lesson10;

import java.awt.event.*;

import java.awt.*;

public class DrawTest {

DrawPanel panel;

DrawControls controls;

Frame Shapes = new Frame("Basic Shapes");

DrawPanel panel = new DrawPanel();

DrawControls controls = new DrawControls(panel);

Shapes.add("Center", panel);

Shapes.add("West",controls);

Shapes.setSize(400,300);

Shapes.setVisible(true);

Shapes.addWindowListener(new WindowAdapter(){

public void windowClosing(WindowEvent e) {

System.exit(0);

The DrawPanel program

package Group.Lesson10;

import java.awt.*;

public class DrawPanel extends Panel {

public static final int NONE = 0;

public static final int RECTANGLE = 1;

public static final int CIRCLE = 2;

public static final int SQUARE = 3;

public static final int TRIANGLE = 4;

int mode = NONE;

public DrawPanel() {

setBackground(Color.white);

The DrawPanel program (continued)

public void setDrawMode(int mode) {

switch (mode) {

case NONE:

case RECTANGLE:

this.mode = mode;

case SQUARE:

this.mode = mode;

break;

case CIRCLE:

this.mode = mode;

break;

case TRIANGLE:

this.mode = mode;

break;

repaint();

The DrawPanel program (continued)

public void paint(Graphics g) {

if (mode == RECTANGLE) {

g.fillRect(100, 60, 100,150);

if (mode == CIRCLE) {

g.fillOval(100, 90, 100, 100);

if (mode == SQUARE) {

g.fillRect(100, 90, 100, 100);

if (mode == TRIANGLE) {

int xpoints[] = {90, 150, 210};

int ypoints[] = {90, 200, 90};

int points = 3;

g.fillPolygon(xpoints, ypoints, points);

Methods Used

fillRect(int x, int y, int width, int height)

fillOval(int x, int y, int width, int height)

fillPolygon(Polygon p)

The DrawControl program (continued)

package Group.Lesson10;

import java.awt.*;

class DrawControls extends Panel implements ItemListener {

DrawPanel target;

Panel NorthPanel = new Panel();

Panel CenterPanel = new Panel();

Panel SouthPanel = new Panel();

private static int Shape = 0;

private static Color targetColor = Color.red;

public DrawControls(DrawPanel target) {

this.target = target;

setLayout(new BorderLayout());

setBackground(Color.lightGray);

target.setForeground(Color.red);

NorthPanel.setBackground(Color.lightGray );

NorthPanel.setLayout(new GridLayout(6,1));

add(NorthPanel, BorderLayout.NORTH);

CheckboxGroup group = new CheckboxGroup();

Checkbox b;

NorthPanel.add(new Label(" Shapes "));

NorthPanel.add(b = new Checkbox("Rectangle", group, false));

b.addItemListener(this);

NorthPanel.add(b = new Checkbox("Circle", group, false));

NorthPanel.add(b = new Checkbox("Square", group, false));

NorthPanel.add(b = new Checkbox("Triangle", group, false));

CenterPanel.setLayout(new GridLayout(4,1));

add(CenterPanel,BorderLayout.CENTER);

CenterPanel.add(new Label(" Colors "));

Choice colors = new Choice();

colors.addItemListener(this);

colors.addItem("red");

colors.addItem("green");

colors.addItem("blue");

colors.addItem("pink");

colors.addItem("orange");

colors.addItem("black");

colors.setBackground(Color.white);

CenterPanel.add(colors);

SouthPanel.setLayout(new GridLayout(4,3));

add(SouthPanel, BorderLayout.SOUTH);

Button CLEAR = new Button("CLEAR");

Button DRAW = new Button("DRAW");

CLEAR.addMouseListener(new MouseAdapter(){

public void mouseClicked(MouseEvent event){

onCommand(1);

DRAW.addMouseListener(new MouseAdapter(){

public void mouseClicked(MouseEvent event){

onCommand(2);

SouthPanel.add(CLEAR);

SouthPanel.add(DRAW);

private void onCommand(int btnNUMBER) {

switch(btnNUMBER){

case 1:

target.setForeground(Color.white);

target.setDrawMode(0);

break;

case 2:

target.setForeground(targetColor);

target.setDrawMode(Shape);

break;

public void itemStateChanged(ItemEvent e) {

if (e.getSource() instanceof Checkbox) {

Checkbox b = new Checkbox();

b = (Checkbox)e.getSource();

if ( b.getLabel().equals("Rectangle") ){

Shape = 1;

} else if ( b.getLabel().equals("Circle") ){

Shape = 2;

} else if ( b.getLabel().equals("Square") ){

Shape = 3;

} else if ( b.getLabel().equals("Triangle") ){

Shape = 4;

if (e.getSource() instanceof Choice) {

String choice = (String) e.getItem();

if (choice.equals("red")) {

targetColor=Color.red;

} else if (choice.equals("green")) {

targetColor=Color.green;

} else if (choice.equals("blue")) {

targetColor=Color.blue;

} else if (choice.equals("pink")) {

targetColor=Color.pink;

} else if (choice.equals("orange")) {

targetColor=Color.orange;

} else if (choice.equals("black")) {

targetColor=Color.black;

Some Features of AWT

• Frames

• Checkbox

• Checkbox Group: Radio Button

• Choice

• Button

Word Bank

• Abstract Class

• Component

• Frame

• Dialog

• Panel

• Layout Manager

End of Lesson 10

SUMMARY

Self-check package Lesson10;

import java.awt.*;

public class MyPanel

Panel WestPanel = new ________; // initialize the panels

Panel CenterPanel = new ________;

Panel EastPanel = new ________;

Panel MainPanel = new ________;

Frame f = new Frame();

WestPanel.setLayout(new ________); // set panel layout

________.____(new Label(" 1 ")); // add item to west panel

________.____(new Label(" 2 "));

________.____(new Label(" 3 "));

________.____(new Label(" 4 "));

________.____(new Label(" 5 "));

________.____(new Label(" 6 "));

CenterPanel.add(new Label(" 1 "));

f.add(WestPanel,___________.______);

f.add(CenterPanel,BorderLayout.CENTER);

f.add(new Label("East"),BorderLayout.EAST);

f.add(new Label("North"),BorderLayout.NORTH);

f.add(new Label("South"),BorderLayout.SOUTH);

f.________(250,250);//set the window size

f.________(true); //allows the panel to be visible

f._______________(new _____________(){// listen for an event in the window

public void windowClosing(WindowEvent e) {

System.exit(0);

End of Lesson 10

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