java object oriented programming (oop)
DESCRIPTION
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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
IDE
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
*/
package Group.Student;
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
Compile Time Error
Compile Time Error
Run-Time Error
Run-Time Error
Word Bank
class
object
interface
message
method
inheritance
encapsulation
compile-time errors
runtime errors
End of Lesson 1
Summary…
End of Lesson 2
Laboratory Exercise
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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
Name
Age
Birthday
//write the methods of the class here
Grow
Give_Name
Get_Name
Get_Age
//write the object name here
Man
//write the data of the object
here
Name: Jonathan
Age: 29
Birthday: March 4, 1975
//write the methods of the object
here
Grow
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
here
//write the methods of the
class here
//write the object name here
//write the data of the object
here
//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
Explaining Welcome.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{
Explaining Welcome.java
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 :
<modifier> <return_type> <method_name>
(<argument_list>) { <statements>) }
Explaining Welcome.java
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);
Explaining Welcome.java
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
/*
This class contains the main() method
*/
public class Main {
public static void main(String args[]) {
Welcome Greet= new Welcome();
Greet.printWelcome();
}
}
Explaining Main.java Line 1-3
Contains a multi-line comment. Anyting in between /* and */ is considered a comment.
/*
This class contains the main() method
*/
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…
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Syntax Review SYNTAX EXAMPLE/S
package <top_package_name>[.<subpackage_name>]*;
package Group.Student;
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>);
Welcome Greet= new Welcome();
< 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
*/
/*
This class contains the main() method
*/
//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.
1 /*
2 This class contains the main() method
3 */
4 package Group.Student;
5
6 public class First {
7 public static void main(String args[]) {
8 Name ____________= new Name();
9 myName.________________();
10 }
11 }
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
7 }
8 }
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
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Java Keywords
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
int 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
type.
• 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
public static void main(String[] args)
{
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
public static void main(String[] args)
{
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);
x++;
++y;
System.out.println("x="+x+"\ny="+y);
--x;
y--;
System.out.println("x="+x+"\ny="+y);
Inc1=x++;
Inc2=++y;
System.out.println("Inc1="+Inc1+"\nInc2="+Inc2);
System.out.println("x="+x+"\ny="+y);
Dec1=--x;
Dec2=y--;
System.out.println("Inc1="+Inc1+"\nInc2="+Inc2);
System.out.println("x="+x+"\ny="+y);
}
}
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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)
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The Relational_operators program output
Logical Operator
Operators Description
! NOT
|| OR
&& 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
Logical Operator- Truth Tables
The XOR (^) operator
Operand1 Operand2 RESULT
true ^ true false
true ^ false true
false ^ true true
false ^ false false
Logical Operator- Truth Tables
The AND (&) operator
Operand1 Operand2 RESULT
true & true true
true & false false
false & true false
false & false false
Logical Operator- Truth Tables
The Logical_operators program package Group.Lesson4.Logical;
public class Logical_operators
{
// Constructor for objects of class Logical_operators
public Logical_operators(){}
public static void main(String[] args)//execution begins here
{
//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)
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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
Operators Description
~ Complement
& AND
| OR
^ XOR (Exclusive OR)
<< Left Shift
>> Right Shift
>>> Unsigned Right Shift
Bitwise Operator - Truth Tables
The BITWISE COMPLEMENT
Operand1 RESULT
~ 1 0
~ 0 1
The BITWISE OR (|)
Operand1 Operand2 RESULT
1 | 1 1
1 | 0 1
0 | 1 1
0 | 0 0
Bitwise Operator - Truth Tables
The BITWISE XOR (^)
Operand1 Operand2 RESULT
1 ^ 1 0
1 ^ 0 1
0 ^ 1 1
0 ^ 0 0
Bitwise Operator - Truth Tables
The BITWISE AND (&)
Operand1 Operand2 RESULT
1 & 1 1
1 & 0 0
0 & 1 0
0 & 0 0
Bitwise Operator - Truth Tables
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() { }
public static void main(String[] args)//execution begins here
{
//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
Operators Description
+= 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
Shift
The Shorthand_operators program
package Group.Lesson4.Shorthand;
public class Shorthand_operators
{ //Constructor for objects of class Shorthand_operators
public Shorthand_operators(){ }
public static void main(String[] args)//execution begins here
{ //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
bit
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
Type
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>)
{
<statement/s>
}
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>){
<statement/s>
}
else
{
<statement/s>
}
package Lesson5.If_Else;
import java.io.*;
public class IfElse {
public IfElse() { }
public static void main(String[] args)throws IOException
{
BufferedReader dataIn=new BufferedReader(new InputStreamReader(System.in));
//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>){
<statement/s>
}
else if (<boolean condition is true>) {
<statement/s>
}
else
{
<statement/s>
}
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
{
BufferedReader dataIn=new BufferedReader(new InputStreamReader(System.in));
//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
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);
}
}
}
The NestedIf program and output
switch Statement
Syntax: switch(<expression>) {
case <constant1>:
<statements>
break;
case <constant2>:
<statements>
break;
:
:
default:
<statements>
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>) {
<statement/s>
}
if(x!=0){
x=(int)x/2;
}
if (<boolean condition is
true>){
<statement/s>
}
else
{
<statement/s>
}
if (A%2==0) {
System.out.println (A+" is EVEN");
}
else
{
System.out.println (A+" is ODD ");
}
Syntax Review SYNTAX EXAMPLE/S
if (<boolean condition is true>){
<statement/s>
}
else if (<boolean condition is true>) {
<statement/s>
}
else{
<statement/s>
}
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);
}
switch(<expression>) {
case
<constant1>:<statements>
break;
case
<constant2>:<statements>
break;
:
:
default:
<statements>
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
public static void main(String[] args)
{
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!”);
}
else
{
System.out.println (number+" is a NEGATIVE number!”);
}
}
}
Loops
Lesson 6
General Topics
• for structure
• while structure
• do-while structure
loop
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>)
{
<statement/s>
}
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() { }
public static void main(String[] args)
{
for(int Ctr=1;Ctr<=5;Ctr++){
System.out.println(Ctr);
}
}
}
while loop
Syntax: while (boolean condition is true)
{
<statement/s>
}
Example:
int Ctr=1;
while(Ctr<=5){
System.out.println(Ctr);
Ctr++;
}
Sample Code and output
public class While_Loop
{
//Constructor for objects of class While_loop
public While_Loop() { }
public static void main(String[] args)
{
int Ctr=1;
while(Ctr<=5){
System.out.println(Ctr);
Ctr++;
}
}
}
do-while loop
Syntax: do {
<statement/s>
} while (<boolean condition is true>);
Example:
int Ctr=1;
do{
System.out.println(Ctr);
Ctr++;
}while(Ctr<=5);
Sample Code
public class DoWhile
{
public DoWhile() { }
public static void main(String[] args)
{
int Ctr=1;
do{
System.out.println(Ctr);
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
them.
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
*/
public static void main(String[] args)
{
for(int Ctr=____;Ctr<=_____;Ctr____){
System.out.println(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
*
* @param String[] args
* @return nothing
*/
public static void main(String[] args)
{
int Ctr=________;
do{
System.out.println(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
*
* @param String[] args
* @return nothing
*/
public static void main(String[] args)
{
int Ctr=____________;
while(Ctr<=__________){
System.out.println(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
loop.
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).
Nested_For loops – how it behaves
Then, click on the
Ok button.
Nested_For loops – how it behaves
– how it behaves
Nested_For loops – 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
Continue_Loop
public class Continue_Loop
{
// Constructor for objects of class Continue_Loop
public Continue_Loop(){ }
public static void main(String [] args)
{
for(int Row=1;Row<=10;Row++){
for(int Column=1;Column<=10;Column++){
if(Column==4){
continue;
}
System.out.print(Row*Column+"\t");
}
System.out.println();
}
}
}
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(){ }
public static void main(String [] args)
{
for(int Row=1;Row<=10;Row++){
for(int Column=1;Column<=10;Column++){
if(Column==4){
break;
}
System.out.print(Row*Column+"\t");
}
System.out.println();
}
}
}
Labels
public class Labels
{
//Constructor for objects of class Labels
public Labels() { }
public static void main(String [] args)
{
here: for(int Row=1;Row<=10;Row++){
for(int Column=1;Column<=10;Column++){
System.out.print(Row*Column+"\t");
if(Column==4){
break here;
}
}
System.out.println();
}
}
}
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 (){ }
public static void main(String [] args)
{
int Row=_______; //indicate the initial value
while(Row<____){
Row++;
int Column=_____; //indicate the initial
value
while(Column<_____){
Column++;
System.out.print(Row*Column+"\t");
}
System.out.println();
}
}
}
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
do{
Row++;
int Column=_____; //indicate the
initial value
do{
Column++;
if(_______){
continue;
}
System.out.print(Row*Column+"\t");
} while(Column<_____);
System.out.println();
} while(Row<____);
}
}
LESSON 7
Exceptions
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
try
catch
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>] {
<declaration/s>
}
Example:
public class Student extends Person
Syntax
<modifier> class <name>
[extends <superclass>]
[implements <interfaces>] {
<declaration/s>
}
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);
System.out.println();
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;
case 2:if((this_Day>=1)&&(this_Day<=28)){day = this_Day;}
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);
if((yearlvl<=4)&&(yearlvl>=1)){
this.yearlvl=yearlvl;
} 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.");
System.out.println();
}
The Student program (continued)
//accessor methods
public void setYearlvl(int yearlvl){
if((yearlvl<=4)&&(yearlvl>=1)){
this.yearlvl=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 ");
birthday.print_Date();
System.out.println("You are "+age+" years old.");
System.out.println();
}
The Student program (continued)
public void setDetails(String name, int age, Date birthday, int
yearlvl){
super.setDetails(name,age,birthday);
if((yearlvl<=4)&&(yearlvl>=1)){
this.yearlvl=yearlvl;
} else {
this.yearlvl=1;
}
System.out.print("Hello, "+name+". ");
System.out.print(" Your birthday this year is on ");
birthday.print_Date();
System.out.println("You are "+age+" years old.");
System.out.println();
}
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 ");
birthday.print_Date();
System.out.println("You are "+age+" years old.");
System.out.println();
}
//accessor methods
public void setSalary(double salary) {
this.salary = salary;
}
The Teacher program (continued)
public void setDetails(String name, int age, Date birthday, double salary){
super.setDetails(name, age, birthday);
this.salary = salary;
System.out.println("Good afternoon, "+name+". Your salary is "+salary+".");
System.out.println(" Your birthday this year is on ");
birthday.print_Date();
System.out.println("You are now "+age+" years old.");
System.out.println();
}
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>
[extends <superclass>]
public class Student
extends Person
<modifier> class <name>
[extends <superclass>]
[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: ");
print_Single_Array(GradeLevel);
for(int Index=1;Index<GradeLevel.length;Index++){
GradeLevel[Index]=Index*2;
}
System.out.print("The contents of the GradeLevel array after
assigning values: ");
print_Single_Array(GradeLevel);
}
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(", ");
}
}
System.out.println();
}
}
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:
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;
case 2:if((this_Day>=1)&&(this_Day<=28)){day = this_Day;}
else {day=1;}
break;
}
} else { month=1; }
year=2005;
}
The Date program (continued)
public static void main(String[] args)
{
Date[] Birthdays={ new Date(23,10), new Date(22,3) };
Date[] Holidays=new Date[4];
Holidays[0]=new Date(25,12);
Holidays[1]=new Date(1,5);
Holidays[2]=new Date(1,11);
Holidays[3]=new Date(1,1);
}
}
The Two_Dimensional_Array program
public class Two_Dimensional_Array
{ //Constructor for objects of class Two_Dimensional_Array
public Two_Dimensional_Array() { }
public static void main(String[] args)
{
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];
Student [1]=new String [2];
Student [2]=new String [1];
Student [3]=new String [1];
//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)
public static void main(String[] args)
{
Date[] Birthdays={ new Date(23,10), new
Date(22,3) };
Date[] Holidays=new Date[4];
Holidays[0]=new Date(25,12);
Holidays[1]=new Date(1,5);
Holidays[2]=new Date(1,11);
Holidays[3]=new Date(1,1);
}
}
Multi-Dimensional Array
SYNTAX:
<data_type> [ ][ ] <array_identifier> =
new <data_type>[<size1>][<size2>];
<data_type> <array_identifier> [ ] [ ]
= new
<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(", ");
}
}
System.out.println();
}
}
Self-check 2
public class Array2
{
// Constructor for objects of class Array2
public Array2 (){ }
public static void main(String[] args)
{
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
GUI
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
vgap)
Examples:
setLayout(FlowLayout());
setLayout(FlowLayout(FlowLayout.LEF
T));
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;
public static void main(String args[]) {
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.event.*;
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.event.*;
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));
The DrawControl program (continued)
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));
b.addItemListener(this);
NorthPanel.add(b = new Checkbox("Square", group, false));
b.addItemListener(this);
NorthPanel.add(b = new Checkbox("Triangle", group, false));
b.addItemListener(this);
The DrawControl program (continued)
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);
The DrawControl program (continued)
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);
}
The DrawControl program (continued)
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;
}
}
The DrawControl program (continued)
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;
}
}
The DrawControl program (continued)
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.event.*;
import java.awt.*;
public class MyPanel
{
public static void main(String args[]) {
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 "));
CenterPanel.add(new Label(" 2 "));
CenterPanel.add(new Label(" 3 "));
CenterPanel.add(new Label(" 4 "));
CenterPanel.add(new Label(" 5 "));
CenterPanel.add(new Label(" 6 "));
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
LABORATORY EXERCISE