Java 8 功能接口不明确引用(这是一个错误吗?
我有两个类似于这些函数的函数:
public static <In extends Number, Out extends Number> Out test(In in, Function<In, Out> f) {
Out x = f.apply(in);
return test(in, x);
}
public static <In extends Number, Out extends Number> Out test(In in, Out out) {
return out;
}
对我来说,很明显,他们不能(!)冲突,而且呼叫不能模棱两可。但是,对于最新版本的 Java 8,以下调用将失败:
Test.test(2, Integer::new);
跟Error:(17, 16) java: reference to test is ambiguous
both method <In,Out>test(In,java.util.function.Function<In,Out>) in org.test and method <In,Out>test(In,Out) in org.test match
而
Test.test(2, new Function<Integer, Number>() {
@Override
public Number apply(Integer integer) {
return 10;
}
});
和
Test.test(2, (Function<Integer, Number>) integer -> 10);
工作。
这是编译器中的错误(还是应该失败?
有关我的设置的更多信息,请参见下文
Java 版本:
Desktop $ java -version
java version "1.8.0_05"
Java(TM) SE Runtime Environment (build 1.8.0_05-b13)
Java HotSpot(TM) 64-Bit Server VM (build 25.5-b02, mixed mode)
错误:
Test.java:5: error: reference to test is ambiguous
Test.test(2, Integer::new);
^
both method <In#1,Out#1>test(In#1,Function<In#1,Out#1>) in Test and method <In#2,Out#2>test(In#2,Out#2) in Test match
where In#1,Out#1,In#2,Out#2 are type-variables:
In#1 extends Number declared in method <In#1,Out#1>test(In#1,Function<In#1,Out#1>)
Out#1 extends Number declared in method <In#1,Out#1>test(In#1,Function<In#1,Out#1>)
In#2 extends Number declared in method <In#2,Out#2>test(In#2,Out#2)
Out#2 extends Number declared in method <In#2,Out#2>test(In#2,Out#2)
测试程序:
import java.util.function.Function;
public class Test {
public static void main(String[] args) {
Test.test(2, Integer::new);
}
public static <In extends Number, Out extends Number> Out test(In in, Function<In, Out> f) {
Out x = f.apply(in);
return test(in, x);
}
public static <In extends Number, Out extends Number> Out test(In in, Out out) {
return out;
}
}
由于其他人确认了该问题,因此我已将其作为错误报告给Oracle。