Sorting issue with 2D array in JAVA

Question

With my following code I try to sort a two dimensional array

 int[][] d2 = {
           {4,5,1},
           {4,1,1},
           {1,7,1},
           {3,3,2},
           {1}
          };

        java.util.Arrays.sort(d2, new java.util.Comparator<int[]>() {
            public int compare(int[] a, int[] b) {
                return a[0] - b[0];
            }
        });

I display the array after sorting

for (int r=0; r<d2.length; r++) {
            for (int c=0; c<d2[r].length; c++) {
                System.out.print(" " + d2[r][c]);
            }
            System.out.println("");
}

The Result I get is like this

 1 7 1
 1
 3 3 2
 4 5 1
 4 1 1

I want the result two come like this

 1
 1 7 1
 3 3 2
 4 5 1
 4 1 1

What is required to be done to get the array sorted like the above?

I tried replacing the {1} with {1,0,0} but it still gives the same result even for {1,0,1} .

Answer 1

Compare the length of passed array in the compare method.. If length of a[] is less than b[] , return -1: -

    java.util.Arrays.sort(d2, new java.util.Comparator<int[]>() {
                public int compare(int[] a, int[] b) {
                    if (a.length != b.length) {
                        return a.length < b.length ? -1 : 1;
                    }
                    return a[0] - b[0];
                }
            });

If you want to sort, by checking each element, which I think you should do this way.. Change your compare method to: -

public int compare(int[] a, int[] b) {

    if (a.length == b.length) {
        for (int i = 0; i < a.length; i++) {
            if (a[i] == b[i]) {

            } else {
                return a[i] - b[i];
            }
        }
        return 0;

    } else {
        return a.length < b.length ? -1 : 1;
    }                       
}

Answer 2

In your Comperator you only use the first field to compare 2 arrays. You have to include all the fields to compare them or at least you have to check the length of the arrays to get your desired result.