为什么静态初始化块中不允许有限定的静态最终变量? [英] Why isn't a qualified static final variable allowed in a static initialization block?

问题描述

class Program {
    static final int var;

    static {
        Program.var = 8;  // Compilation error
    }

    public static void main(String[] args) {
        int i;
        i = Program.var;
        System.out.println(Program.var);
    }
}

案例 2

class Program {
    static final int var;

    static {
        var = 8;  //OK
    }

    public static void main(String[] args) {
        System.out.println(Program.var);
    }
}

为什么案例 1 会导致编译错误?

Why does Case 1 cause a compilation error?

推荐答案

JLS 给出了答案(注意粗体声明):

The JLS holds the answer (note the bold statement):

同样，每个空白的 final 变量最多只能赋值一次；当分配给它时，它必须绝对未分配.这样的赋值被定义为当且仅当变量的简单名称(或者，对于字段，由 this 限定的简单名称)出现在赋值运算符的左侧时发生.[§16]

Similarly, every blank final variable must be assigned at most once; it must be definitely unassigned when an assignment to it occurs. Such an assignment is defined to occur if and only if either the simple name of the variable (or, for a field, its simple name qualified by this) occurs on the left hand side of an assignment operator. [§16]

这意味着在分配静态最终变量时必须使用简单名称" - 即没有任何限定符的 var 名称.

This means that the 'simple name' must be used when assigning static final variables - i.e. the var name without any qualifiers.

这篇关于为什么静态初始化块中不允许有限定的静态最终变量?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！