如何计算排列？ [关闭]

我有一个关于 Java 排列的问题。

Suppose I have five different elements in an array [a, b, c, d, e] and I want to select three elements out of them, the order does matter. I know in math we can use ₅P₃ to get the answer, but can we use Java to get the count and the complete list of elements of the permutation set of ₅P₃?

由于“1,2,3”与“2,1,3”不同，我将建议以下代码片段。请注意，i 不能与 j 或 k 相同，以避免出现“1,1,1”或“1,3,3”的情况。

   // array with elements
   char[] items = {'a', 'b', 'c', 'd', 'e'};
   int count = 0;

    // first of the "three"
    for (int i = 0; i < upperBound; i++) {
       // second of the "three"
       for (int j = 0; j < upperBound; j++) {
          // can't be identical to i
          if (j == i) 
             continue;

          // third of the "three"
          for (int k = 0; k < upperBound; k++) {
             // can't be identical to i or j
             if (k == i || k ==j) 
                continue;

             // print some display
             System.out.println(items[i] + ", " + items[j] + ", " + items[k]);

             // increment the total count
             count++;
          }
       }
    }



    System.out.println("Total count is " + count);