静态变量与Java中的静态类名称相同时会发生什么？ [英] What happens when a Static Variable has the same name as a Static Class in Java?

问题描述

在下面的java示例中，有人可以解释为什么程序的输出是橙色吗？ （这是一个面试问题）

In the java example below, can anyone explain exactly why the output of the program is "Orange" ? (this is an interview question)

public class Finder {
  public static void main(String[] args){
    System.out.println(X.Y.Z);
  }
}

class X {
  static W Y = new W();
  static class Y {
    static String Z ="Apple";
  }
}

class W {
  String Z = "Orange";
}

推荐答案

变量Y模糊了类型Y.参见 JLS ：

The variable Y obscures the type Y. See the JLS:

6.4.2。隐藏

6.4.2. Obscuring

一个简单的名称可能出现在上下文中，它可能被
解释为变量，类型或包的名称。在这些
的情况下，§6.5的规则规定变量将被选择为优先于类型的
，并且将优先选择类型为
的类型。因此，有时可能无法通过其简单名称引用
可见类型或包声明。我们说
这样的声明是模糊的。

A simple name may occur in contexts where it may potentially be interpreted as the name of a variable, a type, or a package. In these situations, the rules of §6.5 specify that a variable will be chosen in preference to a type, and that a type will be chosen in preference to a package. Thus, it is may sometimes be impossible to refer to a visible type or package declaration via its simple name. We say that such a declaration is obscured.

符合条件的名称XYZ根据以下方式解析：

The qualified name X.Y.Z is resolved according to:

6.5.2。上下文不明确名称的重新分类

6.5.2. Reclassification of Contextually Ambiguous Names

...

如果名称位于。左侧。被重新分类为TypeName，然后：

If the name to the left of the "." is reclassified as a TypeName, then:

• 如果标识符是TypeName表示的类型的方法或字段的名称这AmbiguousName被重新归类为ExpressionName。

• If the Identifier is the name of a method or field of the type denoted by TypeName, this AmbiguousName is reclassified as an ExpressionName.

否则，如果该标识符是一个成员类型由类型名表示的类型的名称，这AmbiguousName被重新分类作为TypeName。

Otherwise, if the Identifier is the name of a member type of the type denoted by TypeName, this AmbiguousName is reclassified as a TypeName.

否则，发生编译时错误。

Otherwise, a compile-time error occurs.

由于类型和变量的正常命名约定，这在实践中不太可能发生。

This is unlikely to occur in practice because of the normal naming conventions for types and variables.

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