Java泛型难题

Question

这是相关的代码:

public interface Artifact {}    
public interface Bundle implements Artifact {}
public interface Component implements Artifact {}

public interface State<T extends Artifact> {
    void transition(T artifact, State<T> nextState);
}

这允许我定义这个枚举:

enum BundleState implements State<Bundle> {

    A, B, C;

    public void transition(Bundle bundle, State<Bundle> nextState) {}
    }
}

但我想要的方法签名是:

    public void transition(Bundle bundle, BundleState nextState) {}
    }

但这不编译.显然问题在于我如何T在State界面中定义,但我无法弄清楚如何解决它.

谢谢,唐

Answer 1

事情可能开始变得笨拙,但你可以改变State到:

public interface State<T extends Artifact, U extends State<T, U>> {
    void transition(T artifact, U nextState);
}

并将BundleState更改为:

public enum BundleState implements State<Bundle, BundleState> {
    A, B, C;

    public void transition(Bundle bundle, BundleState nextState) {}
}