java - 当本地定义具有不同参数的函数时，无法调用静态导入的重载函数吗？

Question

我有以下简单的 Java 代码:

A.java

import static a.A1.*;
import static a.A2.*;
class Main {
    public static int g() {return 999;}
    static {
        System.out.println("f('a'): " + f('a'));
        System.out.println("f(): " + f());
        //System.out.println("g('a'): " + g('a'));
        System.out.println("g(): " + g());
    }
}

a/A1.java

package a;
public class A1 {
    public static int f(char x) {return 1;}
    public static int g(char x) {return 123;}
}

a/A2.java

package a;
public class A2 {
    public static int f() {return 0;}
}

f 被定义了两次，并带有重载的参数。如您所见，静态导入 f 的两个定义并调用它们是有效的:

$ javac *.java a/*.java && java Main
f('a'): 1
f(): 0
g(): 999
Exception in thread "main" java.lang.NoSuchMethodError: main

但是当我在本地定义 g 并从某处静态导入它时，它不起作用。以下是我在 Main.java 中取消注释第 8 行时的输出:

$ javac *.java a/*.java && java Main
B.java:8: g() in Main cannot be applied to (char)
        System.out.println("g('a'): " + g('a'));
                                        ^
1 error

为什么？

我尝试将本地 g 更改为非静态，并删除对本地 g 的调用:

import static a.A1.*;
import static a.A2.*;
class Main {
    public int g() {return 999;}
    static {
        System.out.println("f('a'): " + f('a'));
        System.out.println("f(): " + f());
        System.out.println("g('a'): " + g('a'));
    }
}

但是没有成功:

$ javac *.java a/*.java && java Main
B.java:8: g() in Main cannot be applied to (char)
        System.out.println("g('a'): " + g('a'));
                                        ^
1 error

Answer 1

发生这种情况是因为类中声明的名为 g 的方法正在隐藏按需静态导入的名为 g 的方法。请参阅JLS §6.4.1 - Shadowing:

A declaration d of a method named n shadows the declarations of any other methods named n that are in an enclosing scope at the point where d occurs throughout the scope of d.