根据int数组的第一个和第二个元素对int数组的数组列表进行排序

Question

ArrayList<int[]> segment = new Arraylist<int[]>();
segment.add(new int[]{2,3,1});
segment.add(new int[]{2,1,1});
segment.add(new int[]{1,1,1});
segment.add(new int[]{2,4,1});
segment.add(new int[]{3,3,1});

What I want to do is sort this ArrayLists according to the first element of each array and if the element is same do the sorting according to the 2nd element of the array/arrays

For instance the above lines of code should be modified to, (1,1,1) (2,1,1) (2,3,1) (2,4,1) (3,3,1)

this is what i have so far in temrs of solving this,

    public static void SortSegment(ArrayList<int[]> segment){
        Collections.sort(segment, new Comparator<int[]>() {
             public int compare(int[] a, int[] b) {
                  return (a[0] - b[0]);
             }
        });
    }

this piece of code sorts the arraylist of int arrays according to the first element of each of the int arrays. How do i modify it to work for cases where the first element is the same so it takes into consideration the 2nd element?

thanks.

Answer 1

Comparator接口在Java 8中具有一些有用的实用程序（默认）方法，这些方法可用于自定义排序：

segment.sort(Comparator.comparingInt(el -> el[0]).thenComparingInt(el -> el[1]));

Answer 2

Try this:

segments.sort(Comparator.comparingInt(a -> a[0])
    .thenComparing(a -> a[1])
    .thenComparing(a -> a[2]));

Answer 3

try this

if(a[0] - b[0]==0) //Like the first row of the matrix if so, we proceed to the next to know which is lower

code complete

Collections.sort(segment, new Comparator<int[]>() {
         public int compare(int[] a, int[] b) {
              if(a[0] - b[0]==0) //if equals
              {
                  return a[1]-b[1];//recompare 
              }
              else
                  return a[0]-b[0];
         }
    });