Generic Classes in Java

[sreekandank]

Generic class is a class with one or more type variables. A Generic class declaration looks like a non-generic class declaration, except that the class name followed by a type parameter. For instance, consider a following generic class Employee<T>.

class Employee<T>
{
 private T obj;
 Employee(T obj)
 {
  this.obj=obj;
 }
 T getObj()
 {
  return obj;
 }
}
 

The Employee class introduces a Type variable T, enclosed in angle brackets <>, after the class name. The type variables can be used throughout the class definition to specify method return types, and the types of variables.

A generic class can have more than one type variables. For example,
class Employee<T,U>

Let's consider the following example program that shows the generic Employee class, and it uses the Type variable T.

class Employee<T>
{
 private T obj;
 Employee(T obj)
 {
  this.obj=obj;
 }
 T getObj()
 {
  return obj;
 }
}
/**
*@author Sreekandan.K
*/
public class GenericEmployeeClass
{
 public static void main(String args[])
 {
  Employee<String> str=new Employee<String>("AAS");
  System.out.println("Name:"+str.getObj());
  Employee<Integer> i=new Employee<Integer>(21);
  System.out.println("Age:"+i.getObj());
  Employee<Double> d=new Employee<Double>(30000.0);
  System.out.println("Salary:"+d.getObj());
 }
}