JAVA EE: Java Tutorial: Java Generics[Define a generic method which accepts Type parameter with single bound]

Tuesday, 16 May 2017

Java Tutorial: Java Generics[Define a generic method which accepts Type parameter with single bound]

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Java Tutorial: Java Generics[Define a generic method which accepts Type parameter with single bound]

Box.java

public class Box<T>
{

    private T t;

    public void set(T t)
    {
        this.t = t;
    }

    public T get()
    {
        return t;
    }

    public <U extends Number> void inspect(U u)
    {
        System.out.println("T: " + t.getClass().getName());
        System.out.println("U: " + u.getClass().getName());
    }

}

GenericDemo.java

public class GenericDemo
{

    public static void main(String[] args)
    {
        Box<Integer> integerBox = new Box<Integer>();
        integerBox.set(new Integer(100));
        integerBox.inspect(new Integer(200));
        System.out.println("-------------------");
        integerBox.inspect(new Double(20.23));
        System.out.println("-------------------");
        integerBox.inspect(new Long(2000));

        /*
         * error: this is still String!
         */
        //integerBox.inspect("some text");

    }

}

Output

T: java.lang.Integer
U: java.lang.Integer
-------------------
T: java.lang.Integer
U: java.lang.Double
-------------------
T: java.lang.Integer
U: java.lang.Long