强制“等于”在界面中 [英] Enforce "equals" in an interface

问题描述

我有一个接口，我希望实现此接口的每个人都实现一个覆盖的equals方法。

I have an interface and I want everyone who implements this interface to implements an overrridden "equals" method.

有没有办法确保发生这种情况？

Is there a way to make sure that happens?

我猜这种情况的方式是实现我的接口的类将自动从Object获取equals，从而使接口满意。

The way I guess this will happen is that the class that implements my interface will automatically get the equals from Object therefore making the interface happy.

推荐答案

不，你只能创建一个抽象类而不是像这样的接口：

No, you only can create an abstract class instead of an interface like this:

public abstract class MyApi {

  public final boolean equals(Object other) {
    if (other == this) {
      return true;
    }
    if (other instanceof MyApi) {
      return equals((MyApi)other);
    }
    return false;
  }

  protected abstract boolean equals(MyApi other);

}

或更简单的版本：

public abstract class MyApi {

  public boolean equals(Object other) {
    throw new UnsupportedOperationException("equals() not overridden: " + getClass());
  }

}

编辑（在@CodeConfident发表评论后试一试，谢谢！从未认为它会起作用）：

EDIT (gave it a try after the comment from @CodeConfident, thanks! Never assumed it would work):

您也可以简单地声明等于（ ）在抽象类中（不在接口中！）因此隐藏 Object 实现并在任何子类中强制执行新实现：

You can also simply declare equals() in an abstract class (not in an interface!) and therefore hide the Object implementation and enforce a new implementation in any subclass:

public abstract class MyApi {

  public abstract boolean equals(Object obj);

  public abstract int hashCode();

}

无论如何，你应该总是实现等于（）和 hashCode（）一起履行合同。

Anyway you should always implement equals() and hashCode() together to fulfil the contract.

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