how to randomize array with rules in java code example

Example: how to randomize an array java

void shuffle(int [] arr) {
        for (int i = 0; i < arr.length; i++) {
            int index = (int) (Math.random() * arr.length);
            int temp = arr[i];
            arr[i] = arr[index];
            arr[index] = temp;
        }
    }