6. Java Program
• Java Application Program
– Application
• Program written in general programming language
– Applet
• Program running in Web Browser Environment
• Can be viewed by appletviewer or Web browser with
JVM
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7. Classes and Objects
• Object
– Memory Space to Define State and Operation
– Instance of Class
• Class
– A class is a template or blueprint for objects. To program in
Java, you must understand classes and be able to write and
use them.
– Template of Creating Object
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8. The Java Class Libraries
• java.applet : Applet related
• java.awt : Abstract Window Toolkit
• java.awt.event : Event process from awt component
• java.awt.image : Image processing
• java.beans : JavaBeans Component
• java.io : File or Network I/O Support
• java.lang : Java Language Support
• java.net : Network related functions
• java.util : Utility function
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10. Variables and Assignments
• Types
– char 16bits Unicode character data
– boolean Boolean Variable
– byte 8 bits signed integer
– short 16 bits signed integer
– int 32 bits signed integer
– long 64 bits signed integer
– float 32 bits signed floating point number
– double 64 bits signed floating point number
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11. Variables and Assignments
• String : sequence of character
String s = “Enter an integer value: ” ;
• Concatenation Operator ‘+’
String s = “Lincoln said: ” + “” Four score and seven years
ago”” ;
Result :
Lincoln said: “Four score and seven years ago”
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12. Comments
• Single Line Comment
– int i = 10 ; // i is counter
• Multiple Line Comment
/*
Some comments
*/
• Documentation Comment
/**
Documentation Comment
*/
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13. Java Keywords
• 50 Java Keywords
abstract double int super
boolean else interface s witch
break extends long synchronized
byte final native this
case finally new throw
catch float package throws
char for private transient*
class goto* protected try
const* if public void
continue implements return volatile
default import short while
do instanceof static strictfp
assert (New in 1.5) enum (New in 1.5)
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14. Control Statement
• A statement represents an action or a sequence of actions.
To change the execution order of program
• As the method of controlling the execution order
– Conditional Statement : if St., switch St.
– Repeat Statement : for St., while St., do-while St.
– Branch Statement : break St., continue St., return St.
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15. For Statement
Repeat the sequence of statement as many as defined.
Form of for statement
for ( <expr. 1> ; < expr. 2> ; < expr. 3>)
<statement>
<expr. 1> : initialize the control variable
<expr. 2> : check the control variable
<expr. 3> : modify the control variable
s = 0;
for (i=1; i<=N; ++i) // sum from 1 to N : i increment
s += i;
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16. Break Statement
• To move control to the out of the block
• From of break statement
break [label] ;
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17. Source Code
Create/Modify Source Code
Compile Source Code
i.e. javac Welcome.java
Bytecode
Run Byteode
i.e. java Welcome
Result
If compilation errors
If runtime errors or incorrect result
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18. Modifiers
Java uses certain reserved words called modifiers that specify
the properties of the data, methods, and classes and how
they can be used.
Examples of modifiers are public and static. Other modifiers are
private, final, abstract, and protected. A public datum,
method, or class can be accessed by other programs. A
private datum or method cannot be accessed by other
programs.
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