java - 所包含的匿名内部类使用的函数的参数由 "final"修改。但为什么？

Question

这个问题已经有答案了:

Why are only final variables accessible in anonymous class? (16 个回答)

已关闭 9 年前。

public Destination destination(final String dest, final float price) {
    return new Destination() {
        private int cost;
        {
            cost = Math.round(price);
            if (cost > 100)
                System.out.prinltn("Over budget!");
        }
        private String label = dest;
        public String readLabel() { return label; }
    };
}

所包含的匿名内部类使用的参数由“final”修饰。但为什么？

Answer 1

关于规则适用于内部类 (JLS 8.1.3) :

Any local variable, formal method parameter or exception handler parameter used but not declared in an inner class must be declared final. Any local variable, used but not declared in an inner class must be definitely assigned before the body of the inner class.

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