接口(两种方法，根据类的不同返回类型)Java [英] Interface (two methods, different return types depending on class) Java

问题描述

任何扩展接口的类都必须实现在接口中声明的方法.不知道这是否可能，但是我想做的是以下事情:

Any class that extends an interface must implement the methods declared in the interface. Not sure if this is possible but what I want to do is the following :

interface test {
   ____ get();
}

class A extends test {
  int val;

  A(int x) {
    val = x;
  }

  int get() {
    return Val;
  } 


  class B extends test {
  String val;

  B(String x) {
    val = x;
  }

  String get() {
    return Val;
  } 

是否有一个方法签名可以返回两种不同的数据类型?

Is it possible to have a method signature that is able to return two different data types?

推荐答案

不是完全一样，但是您可以使用泛型类型参数来接近它.

Not exactly like that but you can get close with a generic type parameter.

interface Test<T> {
    T get();
}

class A implements Test<Integer> {
    int val;

    A(int x) {
        val = x;
    }

    @Override
    public Integer get() {
        return val;
    }
}

class B implements Test<String> {
    String val;

    B(String x) {
        val = x;
    }

    @Override
    public String get() {
        return val;
    }
}

如您所见，您必须使用Integer，因为泛型不适用于原语.

As you can see, you're bound to use Integer because generics don't work with primitives.

还要注意，同一接口的这两个版本现在基本上是2个不同的接口.

Also note, those 2 versions of the same interface are essentially 2 different interfaces now.

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