Java 泛型难题

Question

相关代码如下:

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) {}
    }
}

但是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在 State 界面中定义 T，但我不知道如何修复它。

谢谢， 唐

Answer 1

事情可能开始变得笨拙，但您可以将 State 更改为:

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) {}
}