Implementing abstract methods in a subclass in Java

Question

I've made my code as generic as possible to try and help people in the future. My abstract class has a method of the type class and and an input of the type class. In the class that extends the abstract, I try to implement that method to no avail. What am I doing wrong?

public abstract class A {
    public abstract A method1(A arg);
}

public class B extends A {
    @Override
    public B method1(B arg) { "...insert code here"} // Error: The method method1(B) must override or implement a supertype method
}

Answer 1

To achieve what you want : associating the type of the argument to the declared class, you could use generics.

abstract class :

public abstract class A <T extends A<T>> {
    public abstract T method1(T arg);
}

concrete class :

public class B extends A<B> {
    @Override
    public B method1(B arg) { 
     ...
      return ...
    }
}