Java Generics

It has been observed that many programs or algorithms are same irrespective of data type they are applied to. To overcome this generics were added by JDK 5.Generics allows to define algorithms once which then can be applied to any datatype without any additional effort. Parameterized types can be referred as generics .A generic class is single class which is useful to operate on multiple types of data. Similar to generic class there can be generic method and generic interface.Generics can only work with objects not with primitive types.

Program of Generic class:

package com.java2novice.generics;
 
public class FirstGenerics {
 
    public static void main(String arg[]){
         
        SimpleGeneric<String> obj = new SimpleGeneric<String>("JAVA2NOVICE");// for string datatype
        obj.printType();
        
        SimpleGeneric<Boolean> obj1 = new SimpleGeneric<Boolean>(Boolean.TRUE);// for boolean datatype
        obj1.printType();
    }
}
 
/**
 * Here A is a type parameter, and it will be replaced with 
 * actual type when the object got created. 
 */
class SimpleGeneric<A>
{
    private A objReff = null; //declaration of object type A
    public SimpleGeneric(A param) //constructor to accept type parameter A
    {
        this.objReff = param;
    }
     
    public A getObjReff()
   {
        return this.objReff;
    }
     
 
    public void printType()    //prints the holding parameter type
   {
        System.out.println("Type: "+objReff.getClass().getName());
    }
}

Output