java: boolean instanceOf 布尔值?

2022-01-19 00:00:00 boolean casting java autoboxing primitive

我有点困惑:我有一个函数，它接受一个对象作为参数.但是，如果我只传递一个原语，甚至将布尔原语识别为布尔对象，编译器不会抱怨.为什么呢?

I'm a bit confused: I have a function, that takes an Object as argument. But the compiler does not complain if I just pass a primitive and even recognizes a boolean primitive as Boolean Object. Why is that so? 

public String test(Object value)
{
   if (! (value instanceof Boolean) ) return "invalid";
   if (((Boolean) value).booleanValue() == true ) return "yes";
   if (((Boolean) value).booleanValue() == false ) return "no";
   return "dunno";
}

String result = test(true);  // will result in "yes"

推荐答案

因为原语 'true' 将是 Autoboxed 到 Boolean 并且是一个 Object.

Because primitive 'true' will be Autoboxed to Boolean and which is a Object.

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