Generics in Java

Hello friends,

What is Generics:-

In Generics we can store any type of objects in collection but non-generic we  store only specific type of object.

In generic not need to type casting.But non-generic compulsory to type casting like..

List mylist=new ArrayList();

mylist.add("Samset"); 

String str=(String)mylist.get(0);     //This is typecasting

List<String> mylist=new ArrayList(String);

mylist.add("Samset"); 

String str=mylist.get(0);     //No need typecasting

Example.java

public class Test

{

public static void main(String ar[])

{

List<String> mylist=new ArrayList(String);

mylist.add("Hello"); 

mylist.add("Samset"); 

for(int i=0;i<mylist.size();i++)

{

System.out.println("String data :- "+mylist.get(i));

}

}

}

OUTPUT :- 

String data :-

Hello

Samset

Second Example 

public class Test2

{

   // generic method printArray                         

   public static < E > void printArray( E[] input )

   {

      // Display array elements              

         for ( E element : input ){        

            System.out.printf( "%s ", element );

         }

         System.out.println();

    }

    public static void main( String args[] )

    {

        // Create arrays of Integer, Double and Character

        Integer[] intArray = { 1, 2, 3, 4, 5 };

        Double[] doubleArray = { 1.1, 2.2, 3.3, 4.4 };

        Character[] charArray = { 'W', 'E', 'L', 'C', 'O','M','E' };

        System.out.println( "Array integerArray contains:" );

        printArray( intArray  ); // pass an Integer array

        System.out.println( "\nArray doubleArray contains:" );

        printArray( doubleArray ); // pass a Double array

        System.out.println( "\nArray characterArray contains:" );

        printArray( charArray ); // pass a Character array

    } 

}

OUTPUT :-

Array integerArray contains:

1 2 3 4 5 6

Array doubleArray contains:

1.1 2.2 3.3 4.4 

Array characterArray contains:

W E L C O M E