Question

I am trying to understand what the following means?

public class Bar<T extends Bar<T>> extends Foo<T> {
    //Some code
}

What is the advantage of doing something like this (e.g. use-case?).

Answer 1

That’s a fairly theoretical example, but you could need it in this case:

public class Bar<T extends Bar<T>> extends Foo<T> {

    private final T value;

    public T getValue() { return value; }

    public void method(T param) {
        if (param.getValue().equals(someValue)) {
            doSomething();
        } else {
            doSomethingElse();
        }
    }
}

You would not be able to call param.getValue() if T were not a Bar, which it is because T extends Bar<T>.