Question

I just want to know for what java.util.Collections.checkedList() is actually used.

I have some code that I know is returning me a List<String> but it’s being passed through a chain of messaging calls and returned to me as a java.io.Serializable. Is that checkedList call good for me to turn my Serializable into a List<String>? I know I can cast it to a java.util.List, but I’d rather not have to check each element and I’m not comfortable with assuming each element is a String.

Answer 1

It is used in part as a debugging tool to find where code inserts a class of the wrong type, in case you see that happening, but can’t figure out where.

You could use it as part of a public API that provides a collection and you want to ensure the collection doesn’t get anything in it of the wrong type (if for example the client erases the generics).

The way you could use it in your case is:

 Collections.checkedList(
      new ArrayList<String>(uncertainList.size()), String.class)
      .addAll(uncertainList);

If that doesn’t throw an exception, then you know you are good. That isn’t exactly a performance optimized piece of code, but if the list contents are reasonably small, it should be fine.