为什么此数组不打印所有值（打印0）？

Question

Basically the program generates positions of x,y,z coordinates, including a distance index. The program stores them in each specified index, and proceeds to sort them. The resultant output is sorted but some columns print a bunch of zeroes (As if the array is never generated at that position). Any help would be appreciated!

Example output :

(0.0),(0.0),(0.0)),(0.0)
(0.0),(0.0),(0.0)),(0.0)
(0.0),(0.0),(0.0)),(0.0)
(0.0),(0.0),(0.0)),(0.0)
(0.0),(0.0),(0.0)),(0.0)
(2.1933026),(3.873999),(2.6528487)),(5.1822824)
(2.1933026),(3.873999),(4.9137025)),(6.6304536)
(3.4213266),(5.4315333),(5.976922)),(8.771011)
(4.084449),(5.4315333),(5.976922)),(9.050297)
(6.4669027),(5.4315333),(5.976922)),(10.346303)

Main program

//import java.util.ArrayList;

import java.util.*;
public class MyQuickSort {
  private static float a[][] = new float [10][4];

  public static void main(String[] args) {
    System.out.println("(" + "X Length" + "),(" + "Y Length" + "),(" + "Z Length" + "),(" + "Distance Length" + ")");
    for(int i = 0; i < a.length ; i++) {
      for(int j = 0; j < 3; j++) {
        a[i][j] = (float)(Math.random () * 6) +1 ;
        //a[i][3] = (float)Math.sqrt((a[i][0] * a[i][0]) + (a[i][1] * a[i][1]) + (a[i][2] * a[i][2]));
        for (int k = 0; k < 4; k++ ) {
          quickSort(a, 0, a.length - 1,k);
        }
      }
              a[i][3] = (float)Math.sqrt((a[i][0] * a[i][0]) + (a[i][1] * a[i][1]) + (a[i][2] * a[i][2]));
      System.out.println("(" + a[i][0] + "),(" + a[i][1] + "),(" + a[i][2] + ")" + "),(" + a[i][3] + ")"); 
    }
  }

  public static void quickSort(float[][] a, int p, int r,int k)
  {
    if(p<r)
    {
      int q=partition(a,p,r,k);
      quickSort(a,p,q,k);
      quickSort(a,q+1,r,k);
    }
  }

  private static int partition(float[][] a, int p, int r,int k) {

    float d = a[p][k];
    int i = p-1 ;
    int j = r+1 ;

    while (true) {
      i++;
      while ( i< r && a[i][k] < d)
        i++;
      j--;
      while (j>p && a[j][k] > d)
        j--;

      if (i < j)
        swap(a, i, j,k);
      else
        return j;
    }
  }

  private static void swap(float[][] a, int i, int j, int k) {

    float temp = a[i][k];
    a[i][k] = a[j][k];
    a[j][k] = temp;
  }
}

Answer 1

You've mixed array initialization and sorting - that's the problem. On the first iteration, you fill the first element and then run sort, which moves this element to the end of the array, as it's greater than uninitialized zeros. After sorting you print the first element which is now filled with zeros. This is still happening till the 6th iteration, when number of initialized elements becomes greater than number or uninitialized elements.

You probably want to split the code in three parts: initialization, sorting, and printing.

Answer 2

You sort in the loop. This means the filled values are sorted to the end, and then later overwritten.

Fix: First do the i/j loop to fill, then sort once, then do a separate loop to print the data