Re: Chained call pattern with inheritance, polymorphism and generics...

 Daniel Pitts <>
Sat, 29 Sep 2007 06:24:26 -0000
On Sep 28, 6:57 pm, Roedy Green <>

On Fri, 28 Sep 2007 10:57:44 +0200, Piotr Kobzda <>
wrote, quoted or indirectly quoted someone who said :

What's wrong then with pattern presented by Daniel to achieve that?

I can't make any sense of it.
Roedy Green Canadian Mind Products
The Java Glossary

What if I changed it to this:

public class BaseBuilder<T> {
    private String something;
    public T something(String something) {
       this.something = something;
       return getChainTarget();

    protected abstract T getChainLink();

public class SpecificBuilder extends BaseBuilder<SpecificBuilder> {

    private String other;

    public SpecificBuilder other(String other) {
        this.other = other;

    protected SpecificBuilder getChainLink() {
     return this;

SpecificBuilder b = new

This works since something() returns T, which in SpecificBuilder IS

The problem with my solution is that I can't have:

class MoreSpecificBuilder extends SpecificBuilder {
    public void doMore() {
    protected MoreSpecificBuilder getChainLink() {
     return this;

new MoreSpecificBuilder().something("hello").doMore(); // whoops!

If "something()'s" return type could be "the compile time type of the
reference to this object", a.k.a ThisType, then it would work just
fine. Unfortunately, thats not yet a feature. Makes one long for a
weakly typed language :-)

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