Question

my code is like this:
i have two classes
first class:

public class Box<E> {

E data1;

    public Box(E data) {
        this.data1 = data;
    }
    public E getData() {
        return data1;
    }
}

second class:

public class IntBox extends Box<Integer>{

    Integer data;

    public IntBox(Integer data) {
        this.data = data;
    }

    public Integer getData() {
        return data;
    }
}

why doesn’t this class extend from Box<E>?

Answer 1

That won’t compile.

Your second class should be:

public class IntBox extends Box<Integer>{  
    public IntBox(Integer data) {
        super(data);
    }
}

And then it will properly extend it and use Box’s methods.