Generics

Generics add stability to your code by making more of your bugs detectable at compile time. Some programmers choose to learn generics by studying the Java Collections Framework; after all, generics are heavily used by those classes.

For class Box:

In the following example T can be used like the regular types.

For e.g. T temp, T t, etc, etc…

At a later stage we need to replace T with other data objects such as                 Integer, String etc, when we create objects of class Box…

For class BoxDemo:

Box<Integer> integerBox=new Box<Integer>();//<Integer> replaces every instance of T in the Box class with Integer…

i.e. every T=integer

Once integerBox is initialized, we're free to invoke its get method without providing a cast…

Hence, if we use integerBox.add(“string”) to add a string, it reports a compile time error…

/**

 * Generic version of the Box class.

 */

public class Box<T> {

    private T t; // T stands for "Type"         

    public void add(T t) {

        this.t = t;

    }

    public T get() {

        return t;

    }

}

public class BoxDemo {

        public static void main(String[] args) {

        Box<Integer> integerBox = new Box<Integer>();

        integerBox.add(new Integer(10));

        Integer someInteger = integerBox.get(); // no cast!

        System.out.println(someInteger);

    }

}