java.lang.ClassCastException: [Ljava.lang.Object; incompatible with [Ljava.lang.String;

Question

I am trying to retrieve random elements from a linkedhashset. Below is my code but it is giving me exception everytime.

private static void generateRandomUserId(Set<String> userIdsSet) {

    Random rand = new Random(System.currentTimeMillis());
    String[] setArray = (String[]) userIdsSet.toArray();
    for (int i = 0; i < 10; ++i) {
        System.out.println(setArray[rand.nextInt(userIdsSet.size())]);
    }
}

Below is the exception I am getting-

java.lang.ClassCastException: [Ljava.lang.Object; incompatible with [Ljava.lang.String;

Can anyone help me on this? And is there any better way of doing this?

Answer 1

Try this:

String[] setArray = userIdsSet.toArray(new String[userIdsSet.size()]);

the toArray method that takes no arguments returns an Object[] which can't be cast to a String[] . The other version returns a typed array.