为什么Java不允许用实例方法隐藏静态方法?

As shown in http://docs.oracle.com/javase/tutorial/java/IandI/override.html, Java does allow

如http://docs.oracle.com/javase/tutorial/java/IandI/override.html所示，Java是允许的

Overriding an instance method by an instance method and
用实例方法重写实例方法。
Hiding a static method by a static method
用静态方法隐藏静态方法

My question is why Java doesn't allow hiding a static superclass method by an instance method. This could be done like this:

我的问题是为什么Java不允许用实例方法隐藏静态超类方法。可以这样做:

class Base {
    static void foo () {}
}

class Derived extends Base {
    void foo () {}
    void access () {
        foo ();
        Base.foo ();
    }
}

I don't see any particular issue with the above approach - it is only as "messy/complex" as the (allowed) hiding of statics already is.

我不认为上述方法有什么特别的问题——它只是像(允许的)静态隐藏一样“混乱/复杂”。

4 个解决方案

#1

I suspect it is to avoid confusion with dealing with the base class. In fact I imagine the designers didn't see an obvious way this should behave.

我怀疑这是为了避免处理基类时的混乱。事实上，我想设计师们并没有看到这种行为的明显方式。

class Base {
    static void foo () {}
}

class Derived extends Base {
    void foo () {} // say this compiled
}

Base b = new Derived()
b.foo(); // should the static or the virtual method be called?

Should b.foo() call Base.foo() or should it potentially call Derived.foo()?

b.foo()应该调用Base.foo()，还是应该调用Derived.foo()?

#2

Simple answer: that would be the mess.

简单的回答是:那将是一团糟。

Concrete answer: what to call in that case Derived.foo()? Base.foo() can't be called as it's hidden (as per you), Derived.foo() can't be called as it's not static.

具体答案:在这种情况下，调用什么?Base.foo()不能被调用，因为它是隐藏的(根据您的要求)，Derived.foo()不能被调用，因为它不是静态的。

#3

Because, one are like Bananas and the other ones are Apples.

因为，一个像香蕉，另一个像苹果。

Explaination:

解释:

Static Methods are created when reading the Class-Structure
静态方法是在读取类结构时创建的。
Methods are created when a object of a class is created.
方法是在创建类的对象时创建的。

Example:

例子:

Foo.bar();

is something different than

是不同于

new Foo().bar();

Guess which one is called?

猜猜叫什么名字?

Foo f = new Foo();
f.bar();

#4

Another to add here is: 1. Static methods belong at the class level. So u cannot override method in the derived class. as simple its called hiding. :) 2. Instance methods belong to the objects, so objects are overrided. So we can override in the derived class.

另一个要加的是:1。静态方法属于类级别。所以u不能重写派生类中的方法。简单地说就是隐藏。:2)。实例方法属于对象，因此对象被覆盖。我们可以重写派生类。

Above other comments give a good example have a look into it..

上面的其他评论给出了一个很好的例子。

Regards Punith

问候Punith

#1