GenDemo.java

package chapter14;

//A simple Generic Class
//Here , T is a type parameter that
//will be replaced by a real type
//when an object of type Gen is created

class Gen<T> {
    T ob; //declare an object of type T

    //Pass the constructor a reference to
    //an object of type T
    Gen(T o) {
        ob = o;
    }

    //Return ob
    T getOb() {
        return ob;
    }

    //Show type of T
    void showType() {
        System.out.println("Type of T is " + ob.getClass().getName());
    }
}

//Demonstrate the generic class
public class GenDemo {
    public static void main(String[] args) {
        Gen<Integer> iOb;

        //Create a Gen<Integer> object and assign its
        //reference to iOb. Notice the use of autoboxing
        //to encapsulate the value 88 within an Integer object
        iOb = new Gen<Integer>(88);

        //Show the type of data used by iOb
        iOb.showType();

        //Get the value in iOb
        int v = iOb.getOb();
        System.out.println("value : " + v);

        System.out.println();

        //Create a Gen object for Strings
        Gen<String> strOb = new Gen<String>("Generic Test");
        //Show the type of data used b strOb
        strOb.showType();

        //Get the value of strOb, notice
        //that cast is not needed.
        String str = strOb.getOb();
        System.out.println("value : " + str);
    }
}