public static void printUnorderedPairs(int[] array) {
    for(int i = 0; i < array.length - 1; i++)
      for(int j = i + i; j < array.length; j++)
        System.out.println("(" + array[i] + ", " + array[j] + ")");
}

/*
 Note that 1 + 2 + 3 + 4 + 5 + ..+ n = (n * (n + 1)) / 2
*/