getClass() of a Generic Method Parameter in a Java

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日久生厌
日久生厌 2021-02-14 17:24

The following Java method fails to compile:

 void foo(T t)
{
    Class klass = t.getClass();
}

Error

2条回答
  •  粉色の甜心
    2021-02-14 18:01

    Because the T class' type doesn't extend from T. Instead, it extends from Number, exactly as you have declared yourself in . Simple as that.

    A better question would be:

    Why doesn't the following compile?

     void foo(T t)
    {
        Class class1 = t.getClass();
    }
    

    The answer to that is that the Object#getClass() returns Class with an unbounded wildcard ? because the object itself is not directly aware about its generic type which is been expected in an arbitrary method.

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