The `Arrays.asList()` API returns an instance of `List`. Calling the `toArray()` method on that `List` instance is specified always to return `Object`, that is, an array of `Object`. In previous releases, it would sometimes return an array of some subtype. Note that the declared return type of `Collection.toArray()` is `Object`, which permits an instance of an array of a subtype to be returned. The specification wording, however, clearly requires an array of `Object` to be returned.
The `toArray()` method has been changed to conform to the specification, and it now always returns `Object`. This may cause code that was expecting the old behavior to fail with a `ClassCastException`. An example of code that worked in previous releases but that now fails is the following:
List<String> list = Arrays.asList("a", "b", "c");
String array = (String) list.toArray();
If this problem occurs, rewrite the code to use the one-arg form `toArray(T)`, and provide an instance of the desired array type. This will also eliminate the need for a cast.
String array = list.toArray(new String);