覆盖方法可以具有与基类中不同的访问说明符吗？ [英] Can an overriding method have a different access specifier from that in the base class?

问题描述

在抽象类中，哪个访问修饰符必须用于
方法，以便子类可以决定是否应将其公开？

Which access modifier, in an abstract class, do I have to use for a method, so the subclasses can decide whether it should be public or not? Is it possible to "override" a modifier in Java or not?

public abstract class A {

    ??? void method();
}

public class B extends A {
    @Override
    public void method(){
        // TODO
    }
}

public class C extends B {
    @Override
    private void method(){
        // TODO
    }
}

我知道，如果有人呼叫
，静态绑定会出现问题：

I know that there will be a problem with static binding, if someone calls:

// Will work
A foo = new B()
foo.method();

// Compiler ?
A foo = new C();
foo.method();

但是也许还有另一种方法。我该如何实现？

But maybe there is another way. How I can achieve that?

推荐答案

可以放松限制，但不能使其更加严格：

It is possible to relax the restriction, but not to make it more restrictive:

public abstract class A {
    protected void method();
}

public class B extends A {
    @Override
    public void method(){    // OK
    }
}

public class C extends A {
    @Override
    private void method(){    // not allowed
    }
}

使用原始方法 private 也不起作用，因为这种方法不是在子类中可见，因此不能被覆盖。

Making the original method private won't work either, since such method isn't visible in subclasses and therefore cannot be overriden.

我建议使用 interface s选择性地公开或隐藏方法：

I would recommend using interfaces to selectively expose or hide the method:

public interface WithMethod {
    // other methods
    void method();
}

public interface WithoutMethod {
    // other methods
    // no 'method()'
}

public abstract class A {
    protected void method();
}

public class B extends A implements WithMethod {
    @Override
    public void method(){
      //TODO
    }
}

public class C extends B implements WithoutMethod {
    // no 'method()'
}

...然后只能通过接口使用实例。

... then only work with the instances through the interfaces.

这篇关于覆盖方法可以具有与基类中不同的访问说明符吗？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！