java 将 Object 数组转换为 String 数组会抛出 ClassCastException
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Casting Object array into String array throws ClassCastException
提问by Script_Junkie
List<String> list = getNames();//this returns a list of names(String).
String[] names = (String[]) list.toArray(); // throws class cast exception.
I don't understand why ? Any solution, explanation is appreciated.
我不明白为什么？任何解决方案，解释表示赞赏。
回答by dasblinkenlight
This is because the parameterless toArrayproduces an array of Objects. You need to call the overload which takes the output array as the parameter, and pass an array of Strings, like this:
这是因为无参数toArray产生了一个Objects数组。您需要调用将输出数组作为参数的重载，并传递一个Strings数组，如下所示：
String[] names = (String[]) list.toArray(new String[list.size()]);
In Java 5 or newer you can drop the cast.
在 Java 5 或更新版本中，您可以删除强制转换。
String[] names = list.toArray(new String[list.size()]);
回答by dasblinkenlight
You are attempting to cast from a class of Object[]. The class itself is an array of type Object. You would have to cast individually, one-by-one, adding the elements to a new array.
您正在尝试从Object[]. 类本身是一个类型为 的数组Object。您必须逐个进行转换，将元素添加到新数组中。
Or you could use the method already implemented for that, by doing this:
或者你可以使用已经实现的方法，这样做：
list.toArray(new String[list.size()]);
