java – 为什么我们可以拥有静态最终成员但是在内部类中不能使用

public class Outer {
    static String world() {
        return "world!";
    }
    static class Inner {
        static String helloWorld() {
            return "Hello " + Outer.world();
        }
    }   
    public static void main(String args[]) {
        System.out.println(Outer.Inner.helloWorld());
        // prints "Hello world!"
    }
}

但是,确切地说,根据JLS术语(8.1.3),Inner被称为嵌套类：

Inner classes may inherit static members that are not compile-time constants even though they may not declare them. Nested classes that are not inner classes may declare static members freely,in accordance with the usual rules of the Java programming language.

而且,内部类可以拥有静态最终成员并不完全正确;更确切地说,它们也必须是编译时常量.以下示例说明了不同之处：

public class InnerStaticFinal {
    class InnerWithConstant {
        static final int n = 0;
        // OKAY! Compile-time constant!
    }
    class InnerWithNotConstant {
        static final Integer n = 0;
        // DOESN'T COMPILE! Not a constant!
    }
}

在此上下文中允许编译时常量的原因显而易见：它们在编译时内联.