相关疑难解决方法(0)

假设我们有2节课.一个空类Base,以及该类的子类Derived.

public class Base {}

public class Derived extends Base {}

然后我们在另一个类中有几个方法:

import java.util.Collection

public class Consumer {

    public void test() {
        set(new Derived(), new Consumer().get());
    }

    public <T extends Base> T get() {
        return (T) new Derived();
    }

    public void set(Base i, Derived b) {
        System.out.println("base");
    }

    public void set(Derived d, Collection<? extends Consumer> o) {
        System.out.println("object");
    }

}

这在Java 7中成功编译并运行,但不能在Java 8中编译.错误:

Error:(8, 9) java: reference to set is ambiguous
  both method set(Base,Derived) in Consumer …

使用sourceCompatibility = 1.7或1.6编译时,以下代码有效,但切换到1.8后失败:

public class Java8Wat {
  interface Parcelable {
  }

  static class Bundle implements Parcelable {
    public void put(Parcelable parcelable) {
    }

    public void put(Serializable serializable) {
    }

    public <T extends Parcelable> T getParcelable() {
      return null;
    }
  }

  static {
    Bundle inBundle = new Bundle();
    Bundle outBundle = new Bundle();

    outBundle.put(inBundle.getParcelable());
  }
}

编译输出:

Java8Wat.java:23: error: reference to put is ambiguous
        outBundle.put(inBundle.getParcelable());
             ^
both method put(Parcelable) in Bundle and method put(Serializable) in Bundle match

这是代码失败的回购:https://github.com/chalup/java8-wat …