Java For Beginners

What is Java?

1.It is Object Oriented Programming Language. 2.It is platform independent. 3.It has automatic memory management.

What is Object Oriented Programming?

It has 5 properties. 1.Abstraction 2.Encapsulation 3.Inheritance 4.Modularity 5.Polymorphism

What are the things you need to run a java program?

1.JDK software (available in http://java.sun.com/javase/downloads/index_jdk5.jsp) 2.Set the environmental variables

How to set the environmental variables

There are two methods. First Method: 1.Right click on My Computer,and select properties. 2.Select the Advanced tab. 3.Click on Environmental variables button on the bottom. 4.In the System Variables, click on New button. 5.Set Variable Name : CLASSPATH Variable Value :C:\jdk1.5\lib; and click OK. 6.Again click New Button. 7.Set Variable Name : PATH Variable Value :C:\jdk1.5\bin; and click OK. Second Method: 1.Goto command prompt and navigate to the corresponding folder. 2.set path=c:\jdk1.5\bin; 3.set classpath=c:\jdk1.5\lib;.;

How to write a java program?

1.Open Notepad 2.Write the program 3.Save it with .java extension

Important things to be noted while writing a Java Program

1.Java is case sensitive. 2.Be careful with the filenames,it should match with the class names(case). 3.There should semicolon after every statement.

General Structure of a Java program

public class CLASSNAME {  public void METHODNAME(){     //method body  }  public static void main(String args[]){     //body  } }

Hello World

public class HelloWorld{  public static void main(String args[]){     System.out.println("Hello World");  } } c:\>java HelloWorld Hello World

Command Line Arguments

public class CmdArgs{   public static void main(String args[]){     System.out.println("The first argument is " + args[0]);   } } c:\>java CmdArgs Hello Hello

Usage of If-else

public class ExIf{   public static void main(String args[]){     if(args[0].equals("args")){       System.out.println("You entered args");     }     else{       System.out.println("You did not enter args");     }   } } c:\>java ExIf args You entered args

Usage of For loop

public class ExFor{   public static void main(String args[]){     for(int i=1;i<=args.length;i++){       System.out.println("The " + i + "th argument is " + args[i-1]);     }   } } c:\>java ExFor One Two Three The 1th argument is One The 2th argument is Two The 3th argument is Three

Usage of while loop

public class ExWhile{   public static void main(String args[]){     int i=1;     while(i<=args.length){       System.out.println("The " + i + "th argument is " + args[i-1]);       i++;     }   } } c:\>java ExWhile One Two Three The 1th argument is One The 2th argument is Two The 3th argument is Three