Generics were added by JDK 5. By
using generics you can define an algorithm once, and you can apply it on any
kind of datatype without any additional effort.
At very high level, generics are
nothing but parameterized types. Generics helps us to create a single class,
which can be useful to operate on multiple data types. A class, interface or a
method that operates on a parameterized type is called generics class, interface
or method. Generics adds type safty. Remember that generics only works on
objects, not primitive types.
Example-
package com.netparam.generics;
public class MySimpleGenerics {
public
static void main(String a[]){
//we
are going to create SimpleGeneric object with String as type parameter
SimpleGeneric<String>
sgs = new SimpleGeneric<String>("NETPARAM");
sgs.printType();
//we
are going to create SimpleGeneric object with Boolean as type parameter
SimpleGeneric<Boolean>
sgb = new SimpleGeneric<Boolean>(Boolean.TRUE);
sgb.printType();
}
}
/**
* Here T is a type parameter,
and it will be replaced with
* actual type when the object
got created.
*/
class SimpleGeneric<T>{
//declaration
of object type T
private T
objReff = null;
//constructor
to accept type parameter T
public
SimpleGeneric(T param){
this.objReff
= param;
}
public T
getObjReff(){
return
this.objReff;
}
//this
method prints the holding parameter type
public void
printType(){
System.out.println("Type:
"+objReff.getClass().getName());
}
}
Output-
Type
java.lang.String
Type
java.lang.Boolean
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