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javagenericssubclassing

Define generic Type of parent class method depending on subclass Type in Java

Is it possible to dynamically identify T as a return type depending on subclass Type? I want something like the following:

public class Parent {
        public <T extends Parent> T foo() {
                return (T)this;
        }
}

public class Child extends Parent {
        public void childMethod() {
                System.out.println("childMethod called");
        }
}

And then to call:

Child child = new Child();
child.foo().childMethod();

Without defining the type like so:

Child child = new Child();
child.foo().<Child>childMethod(); // compiles fine

Thanks in advance!

Solution

  • You want this:

    public class Parent<T extends Parent<T>> {
    public T foo() {
        return (T)this;
    }
}

public class Child extends Parent<Child> {
    public void childMethod() {
        System.out.println("childMethod called");
    }
}

Child child = new Child();
child.foo().childMethod(); // compiles