Find duplicates in a given array when elements are not limited to a range

public class GFG {
 
    // Function to find the Duplicates,
    // if duplicate occurs 2 times or
    // more than 2 times in
    // array so, it will print duplicate
    // value only once at output
    static void findDuplicates(
      int arr[], int len)
    {
 
        // initialize ifPresent as false
        boolean ifPresent = false;
 
        // ArrayList to store the output
        ArrayList<Integer> al = new ArrayList<Integer>();
 
        for (int i = 0; i < len - 1; i++) {
            for (int j = i + 1; j < len; j++) {
                if (arr[i] == arr[j]) {
                    // checking if element is
                    // present in the ArrayList
                    // or not if present then break
                    if (al.contains(arr[i])) {
                        break;
                    }
 
                    // if element is not present in the
                    // ArrayList then add it to ArrayList
                    // and make ifPresent at true
                    else {
                        al.add(arr[i]);
                        ifPresent = true;
                    }
                }
            }
        }
 
        // if duplicates is present
        // then print ArrayList
        if (ifPresent == true) {
 
            System.out.print(al + " ");
        }
        else {
            System.out.print(
                "No duplicates present in arrays");
        }
    }
 
    // Driver Code
    public static void main(String[] args)
    {
 
        int arr[] = { 12, 11, 40, 12, 5, 6, 5, 12, 11 };
        int n = arr.length;
 
        findDuplicates(arr, n);
    }
}