In java, can one create a fluent extensible class hierarchy with methods that can be invoked in any order?

Question

Can one create an extensible class hierarchy in java whose methods are fluent and can be invoked in any order? (YES! see answer below), even for existing classes wh

Answer 1

I believe there is a way to do this with generics... Syntax is a little less clean than the desired...

Here is the client code...

    B b = B.factoryB();
    b.setA("a").setB("b");

    A ba = A.factoryA();

    ba.setA("a");

Top level (real) class

public  class A extends Chained {
    private String a = null;

    protected A() {
        }

    public S setA(String a) {
        this.a = a;
        return me();
    }
    public static A factoryA() {
        return new A();
    }
}

Example Subclass

public  class B extends A {
    private String b = null;

    B() {
    }

    public S setB(String b) {
        this.b = b;
        return me();
    }
    public static B factoryB() {
        return new B();

    }

}

Helper

public  abstract class Chained {
    // class should be extended like:
    // ... class A extends Chained

    public Chained() {
    }

    public final S me() {
        return (S) this;
    }
}

It's far from perfect and can be made not to work (if you really wanted to)