JAVA Object Oriented Programming (OOP)

Lesson 1

Introduction
to
Object-Oriented
Programming

Prof. Erwin M. Globio, MSIT
Java Training Specialist
http://eglobiotraining.com

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

You can compile your Java code from the
command line.

SYNTAX:
javac <filename>.java
EXAMPLE:
javac Welcome.java

Java is Portable

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

SYNTAX:
java <filename>
EXAMPLE:
java Welcome

Java is Portable

Java code
(*.java)

Java Compiler

bytecodes
(*.class)

Java Virtual
Machine

MAC PC UNIX

IDE: BlueJ

 Download the appropriate version
 Check the system requirements

IDE

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

 Install J2SE 1.4.2 (Java 2 SDK version
1.4.2) or newer first before installing BlueJ

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

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

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 object name here
Class Human Man

//write the data of the class here //write the data of the object
Name here
Age Name: Jonathan
Birthday Age: 29
Birthday: March 4, 1975
//write the methods of the class here //write the methods of the object
Grow here
Give_Name Grow
Get_Name Give_Name
Get_Age Get_Name
Get_Age

[http://www.techfactors.ph] TechFactors Inc. ©2005

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 object name here

//write the data of the object
//write the data of the class here
here
//write the methods of the
object here
//write the methods of the
class 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.

Lesson 2

Your First Java
Program

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{

Line 3 shows the start of the method printWelcome().
Syntax :
<modifier> <return_type> <method_name>
(<argument_list>) { <statements>) }

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 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);
Example:
System.out.println("Welcome to 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

/*
*/

public class Main {
Welcome Greet= new Welcome();
Greet.printWelcome();
}
}

Line 1-3
Contains a multi-line comment. Anyting in
between /* and */ is considered a
comment.

/*
*/


Line 5
Declares the Main class. the brace after the class
indicates the start of the class.

public class Main {

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 {

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();

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();

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

import import School.Section.Student;
<top_package_name>[.<subpackage_name>]. import School.Section.*;
<class_name>;

<modifier> class <class_name> public class First

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

< package_name>.<class_name> <object_name> = School.Section.Student Alma = new
new <package_name>.<class_name>(<arguments>); School.Section.Student ();

<modifier> <return_type> <method_name> public static void main(String args[])
(<argument_list>) { <statements>} {}
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.

First.java //filename

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 }

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.

Name.java //filename

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 }

Lesson 3

Data Types, Literals,
Keywords and
Identifiers

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


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

 You can also declare several variables for
a specific data type in one statement by
separating each identifier with a comma(,)
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;

Constants
Example:
static final String Student_ID=”098774656”;

Syntax for declaring constants:

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

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
{
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

Lesson 4

Java Operators

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);
x++;
++y;
--x;
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;

The Relational_operators program (Continued)
//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 output


Logical Operator

Operators Description
! NOT
|| OR
&& AND
| short-circuit OR

& short-circuit AND

Logical Operator- Truth Tables

The NOT (!) operator

Operand1 RESULT

! true false
! false true


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);

The Logical_operators program (Continued)

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 output


REVIEW
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

Try converting 16 and 27 to bits.

Hope you got these answers:
16=0000000000010000
27=0000000000011011

REVIEW

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!

Example:
4=0000000000000100
-4=1111111111111100

Bitwise Operator

~ 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 (|)


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 x= 0000000000010000
Therefore, ~x=-17. Left_shift=
0000000010000000
x= 0000000000010000 Left_shift = 128
y= 0000000000011011
Or= 0000000000011011 z= 1111111111111100
Right_shift= 1111111111111111
x= 0000000000010000 Right_shift= -1
y= 0000000000011011
And= 0000000000010000 Negative=1111111111111100
Negative=0011111111111111
x= 0000000000010000 Negative= 1073741823
y= 0000000000011011
Xor= 0000000000001011

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;

The Bitwise_operators program (continued)

//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 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
Shift

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");

The Shorthand_operators program (continued)

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 output

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;

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
Type
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>
}

The IfElse program
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");
}
}
}

nested-if Statement

Syntax:
if (<boolean condition is true>){
<statement/s>
}
else if (<boolean condition is true>) {
<statement/s>
}
else
{
<statement/s>
}

nested-if Statement

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);
}

The NestedIf program and output
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
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 Statement

Syntax:
switch(<expression>) {
case <constant1>:
<statements>
break;
case <constant2>:
<statements>
break;
:
:
default:
<statements>
break;
}

switch Statement
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;
}

The Switch_case program
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 (continued) and output
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; }}}

Word Bank

 Wrapper class

End of Lesson 5

Summary…

Syntax Review
SYNTAX EXAMPLE/S
if (<boolean condition is if(x!=0){
true>) { x=(int)x/2;
<statement/s> }
}
if (<boolean condition is if (A%2==0) {
true>){ System.out.println (A+" is EVEN");
<statement/s> }
} else
else {
{ System.out.println (A+" is ODD ");
<statement/s> }
}

SYNTAX EXAMPLE/S
Syntax Review
if (<boolean condition is true>){ if (number1>number2) {
<statement/s> System.out.println (number1+" is greater than "+number2);
} } else if (number1<number2){
else if (<boolean condition is true>) { System.out.println (number1+" is less than "+number2);
<statement/s> } else {//number1==number2
} System.out.println (number1+" is equal to "+number2);
else{ }
<statement/s>
}

switch(<expression>) { switch(Number){
case case 1:System.out.println("One ");
<constant1>:<statements> break;
break; case 2:System.out.println("Two");
case break;
<constant2>:<statements> case 3:System.out.println("Three");
break; break;
: default:System.out.println("Sorry!");
: break;
default:
}
<statements>
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!”);
}
else
{
System.out.println (number+" is a NEGATIVE number!”);
}
}
}

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
Example:
for(int Ctr=1;Ctr<=5;Ctr++){
System.out.println(Ctr);
}

Syntax:
for (<initialization>;<condition>;<increment>)
{
<statement/s>
}

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
Example:
int Ctr=1;
while(Ctr<=5){
Ctr++;
}

Syntax:
while (boolean condition is true)
{
<statement/s>
}

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
Example:
int Ctr=1;
do{
Ctr++;
}while(Ctr<=5);

Syntax:
do {
<statement/s>
} while (<boolean condition is true>);

Sample Code

public class DoWhile
{
public DoWhile() { }
{
int Ctr=1;
do{
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
*/
{
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=________;
do{
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

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();
}
}
}

Nested_For loops – how it behaves
To see how this program behaves at any given time,
we need to set breakpoints. To do that, just click on
line number.

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

Continue_Loop

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
value
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
do{
Row++;
int Column=_____; //indicate the
initial value
do{
Column++;
if(_______){
continue;
}
} while(Column<_____);
} while(Row<____);
}
}

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{
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{
System.out.print(“Enter another value: ”);
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

General Topics

• Classes
• Inheritance
• Interface
• Objects
• Constructors
• Overloading Methods
• Overriding Methods

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);

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; }


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 <superclass>]
extends Person

<modifier> class <name> public class Teacher
[extends <superclass>] extends Person
[implements <interfaces>]
implements Employee

Syntax Review (continued)

SYNTAX EXAMPLE/S

<modifiers> class <class_name>{ public class Person extends Object{
[<attribute_declarations>] //attribute declarations
private String name;
[<constructor_declarations>]
private int age;
[<method_declarations>] 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
I. Use the applications given on our lesson for exercise A and B.

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.

Self-check 2
II. Use this diagram in answering the next exercises.

Self-check

A. Supply all the method signatures
of Plane to the interface
FlyingObject, except for the
constructors.

public interface FlyingObject{

}

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() { }
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: ");
}

The Single_Array program (continued) and
output
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(", ");
}
}
}
}

Single Dimensional Array

SYNTAX:

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

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

Example:
First Element Last Element

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

YearLevel 1 2 3 4

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

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;
}


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

End of Lesson 9

SUMMARY

Syntax Review
SYNTAX EXAMPLE/S

<data_type> [ ] <array_identifier> = new int [ ] GradeLevel=new int [6];
<data_type>[<no_of_elements>];
<data_type> < array_identifier> [ ] = new int GradeLevel [ ] =new int [6];
<data_type>[<no_of_elements>];
<data_type> [ ] < array_identifier> = {< elements int [ ] YearLevel={1,2,3,4};
separated by commas>};
< array_identifier> [<Index>] = <value>; GradeLevel[Index]=Index*2;
<data_type> [ ][ ] <array_identifier> = new String [ ] [ ] TeacherName = new String
<data_type>[<size1>][<size2>]; [YearLevel] [ ];
<data_type> <array_identifier> [ ] [ ] = new String TeacherName [ ] [ ] = new String
<data_type>[<size1>][<size2>]; [YearLevel] [Section];

< array_identifier> [<Index1>] [<Index2>] = TeacherName [0] [0] = "Lesley Abe";
<value>;
System.arraycopy(<Array_source>, System.arraycopy(YearLevel,0,GradeLev
<Array_sourcePosition>, <Array_destination>, el,1,YearLevel.length);
<Array_destinationPosition>,
<numberOfElements>);

Self-check 1
public class Array1
{
//Constructor for objects of class Array1
public Array1() { }
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]= ___________

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());

The DrawTest program
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
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)
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);
}
}
);
}
}

JAVA Object Oriented Programming (OOP)

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