Interface (two methods, different return types depending on class) Java

Question

Any class that extends an interface must implement the methods declared in the interface. Not sure if this is possible but what I want to do is the following :

interface test {
   ____ get();
}

class A extends test {
  int val;

  A(int x) {
    val = x;
  }

  int get() {
    return Val;
  } 


  class B extends test {
  String val;

  B(String x) {
    val = x;
  }

  String get() {
    return Val;
  } 

Is it possible to have a method signature that is able to return two different data types?

Answer 1

Not exactly like that but you can get close with a generic type parameter.

interface Test<T> {
    T get();
}

class A implements Test<Integer> {
    int val;

    A(int x) {
        val = x;
    }

    @Override
    public Integer get() {
        return val;
    }
}

class B implements Test<String> {
    String val;

    B(String x) {
        val = x;
    }

    @Override
    public String get() {
        return val;
    }
}

As you can see, you're bound to use Integer because generics don't work with primitives.

Also note, those 2 versions of the same interface are essentially 2 different interfaces now.