Generics in Java

The Java Generics programming is introduced in J2SE 5 to deal with type-safe objects.

•Before generics, we can store any type of objects in collection i.e. non-generic. Now generics, forces the java programmer to store specific type of objects.

Advantage of Java Generics

•There are mainly 3 advantages of generics.

         They are as follows:

»1) Type-safety : We can hold only a single type of objects in generics. It doesn’t allow to store other objects.

»2) Type casting is not required: There is no need to typecast the object.

»Before Generics, we need to type cast.

List list = new ArrayList();  

list.add("hello");  

String s = (String) list.get(0);//typecasting 

»After Generics, we don't need to typecast the object.

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

list.add("hello");  

String s = list.get(0);  

»3) Compile-Time Checking: It is checked at compile time so problem will not occur at runtime. The good programming strategy says it is far better to handle the problem at compile time than runtime.

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

list.add("hello");  

list.add(32);//Compile Time Error  

 Generic class

•A class that can refer to any type is known as generic class. Here, we are using T type parameter to create the generic class of specific type.

Type Parameters

•The type parameters naming conventions are important to learn generics thoroughly. The commonly type parameters are as follows:

–T - Type

–E - Element

–K - Key

–N - Number

–V – Value

Generic Method

Like generic class, we can create generic method that can accept any type of argument.