接口和继承：“返回类型int不兼容” [英] interface and inheritance: "return type int is not compatible"

问题描述

public interface MyInterface{
    public int myMethod();
}


public class SuperClass {
    public String myMethod(){
        return "Super Class";
    }
}

public class DerivedClass extends SuperClass implements MyInterface {
    public String myMethod() {...}  // this line doesn't compile 
    public int myMethod() {...}     // this is also unable to compile
}

当我尝试编译 DerivedClass 时，它给了我错误

When I try to compile DerivedClass it gives me the error

java: myMethod() in interfaceRnD.DerivedClass cannot override myMethod() in interfaceRnD.SuperClass
  return type int is not compatible with java.lang.String

我应该如何解决这个问题？

How should I solve this issue?

推荐答案

该错误是由于对<$的调用造成的c $ c> myMethod 将不明确 - 应该调用哪两种方法？来自JLS§8.4.2：

The error results from the fact that a call to myMethod will be ambiguous - which of the two methods should be called? From JLS §8.4.2:

在类中使用覆盖等效签名声明两个方法是一个编译时错误。

方法的返回类型不是其签名的一部分，因此您收到的错误是根据上面的陈述。

The return type of a method is not a part of its signature, so you are receiving an error in accordance with the statement above.

假设你不能简单地重命名冲突的方法，在这种情况下你不能使用继承，并且需要使用像作文：

Assuming you can't simply rename the conflicting methods, you can't use inheritance in this case, and will need to use an alternative like composition:

class DerivedClass implements MyInterface {

    private SuperClass sc;

    public String myMethod1() {
        return sc.myMethod();
    }

    public int myMethod() {
        return 0;
    }

}

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