是否允许对“boolean"和“Object"进行相等比较? [英] Equality comparison of `boolean` and `Object` allowed?

问题描述

以下代码

public class TestComparison {
    public static void main(String[] args) throws Exception {
        boolean b = true;
        Object o = new Boolean(true);
        System.out.println("comparison result: "+ 
            (o == b)); // Eclipse complains about this expression
    }
}

使用javac V1.7.0_15 编译没有错误，运行时打印false".但是，Eclipse Juno 抱怨不兼容的操作数类型 Object 和 boolean".

compiles without errors with javac V1.7.0_15, and prints "false" when run. However, Eclipse Juno complains about "Incompatible operand types Object and boolean".

显然javac自动装箱原始布尔值b，然后通过对象相等比较o和自动装箱的b，产生false，而 Eclipse 拒绝进行自动装箱.

Apparently javac autoboxes the primitive boolean b, and then compares o and autoboxed b by object equality, yielding false, while Eclipse refuses to do the autoboxing.

根据 Java 语言规范，哪种行为是正确的?我应该在哪里提交错误?

Which is the right behaviour according to the Java Language Specification? Where should I file a bug?

注意:如果我将 o 的类型更改为 Boolean，事情会按预期工作:Eclipse 接受代码，并且代码打印真实".

Note: If I change the type of o to Boolean, things work as expected: Eclipse accepts the code, and the code prints "true".

ideone.com 上的可运​​行版本

推荐答案

这是您的项目语言级别设置.您可能正在使用具有 Java 6 语义的 Java 7 编译器.我这里没有 Eclipse，但是我在 IntelliJ 中复制了它，当语言级别在 Java 6 上时会出错，即使我使用的编译器是 7.我猜 Eclipse 有相同的.此链接 解释一下.

It's your project language level setting. You are probably using a Java 7 compiler with Java 6 semantics. I don't have Eclipse here, but I reproduced it in IntelliJ, which gave errors when the language level was on Java 6, even though the compiler I used was 7. I guess Eclipse has the same. This link explains it.

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