检查一个对象是否属于Java中的一个类 [英] Check if an object belongs to a class in Java

问题描述

有没有一种简单的方法来验证一个对象是否属于给定的类?例如，我可以这样做

Is there an easy way to verify that an object belongs to a given class? For example, I could do

if(a.getClass() = (new MyClass()).getClass())
{
    //do something
}

但这需要每次都在运行中实例化一个新对象，只是为了丢弃它.有没有更好的方法来检查a"是否属于MyClass"类?

but this requires instantiating a new object on the fly each time, only to discard it. Is there a better way to check that "a" belongs to the class "MyClass"?

推荐答案

instanceof 关键字，如其他答案所述，通常是您想要的.请记住，instanceof 也会为超类返回 true.

The instanceof keyword, as described by the other answers, is usually what you would want. Keep in mind that instanceof will return true for superclasses as well.

如果你想查看一个对象是否是一个类的直接实例，你可以比较这个类.您可以通过getClass() 获取实例的类对象.您可以通过 ClassName.class 静态访问特定的类.

If you want to see if an object is a direct instance of a class, you could compare the class. You can get the class object of an instance via getClass(). And you can statically access a specific class via ClassName.class.

例如:

if (a.getClass() == X.class) {
  // do something
}

在上面的示例中，如果 a 是 X 的实例，则条件为真，但如果 a 是 a 的实例，则条件不成立X 的子类.

In the above example, the condition is true if a is an instance of X, but not if a is an instance of a subclass of X.

比较:

if (a instanceof X) {
    // do something
  }

在 instanceof 示例中，如果 a 是 X 的实例，或者 a 的实例，则条件为真> 是 X 的 子类 的一个实例.

In the instanceof example, the condition is true if a is an instance of X, or if a is an instance of a subclass of X.

大多数时候，instanceof 是对的.

Most of the time, instanceof is right.

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