快速排序霍尔阵列分区

试图弄明白为什么霍尔分区算法总是将数组分成两个正确的部分。在下面的代码中,我扩展了 Hoare algorithm 让我更清楚(详情见评论)

int partition(int[] arr, int leftIndex, int rightIndex) {
  int pivot = arr[(leftIndex + rightIndex) / 2];

  while (leftIndex <= rightIndex) {
    while (arr[leftIndex] < pivot) leftIndex++;
    while (arr[rightIndex] > pivot) rightIndex--;

    // If all numbers at right places, than leftIndex and rightIndex 
    // could point at same array element index
    // So it's means partion done. 
    // We should return leftIndex + 1 cause 
    // rightIndex points at the last element of the left sub array

    if (leftIndex == rightIndex) return leftIndex + 1; 

    if (leftIndex < rightIndex) {
      swap(arr, leftIndex, rightIndex);
      leftIndex++;
      rightIndex--;
    }
  }

  //But here the tricky thing: Why does this "if case" never execute?
  if (leftIndex - 1 > rightIndex) 
    System.out.println("leftIndex - 1 > rightIndex");

  return leftIndex;
}

所以问题是:是否有可能将数组传递给分区函数,从而执行下面的行?

if (leftIndex - 1 > rightIndex) 
  System.out.println("leftIndex - 1 > rightIndex");?