有人可以解释“ClassCastException”在Java？ [英] Can someone explain "ClassCastException" in Java?

问题描述

我读了一些关于ClassCastException的文章，但我不能得到一个好主意。

I read some articles written on "ClassCastException" but I couldn't get a good idea on that. Can someone direct me to a good article or explain it briefly.

推荐答案

直接从API规范 ClassCastException ：

Straight from the API Specifications for the ClassCastException:

抛出表示代码有
尝试将对象强制转换为
子类它不是一个
实例。

Thrown to indicate that the code has attempted to cast an object to a subclass of which it is not an instance.

因此，例如，当试图投射 Integer 到字符串， String 不是 Integer ，因此将抛出 ClassCastException 。

So, for example, when one tries to cast an Integer to a String, String is not an subclass of Integer, so a ClassCastException will be thrown.

Object i = Integer.valueOf(42);
String s = (String)i;            // ClassCastException thrown here.

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