Procedure to sort a two dimensional int array depending on column

Question

The array I have before and how we want it after the sorting:

Before:

Box    Weight    Priority
1       50          5
2       30          8
3       90          6
4       20          7  
5       80          9

After:

Box    Weight    Priority
3       90          6
5       80          9
1       50          5
2       30          8
4       20          7

We work in the int matrix:

data= new int[BoxNumber][3];

The sorting is based in the second column Weight. I am looking for a procedure that sorts the data array.

 public void sortC(int[][] temp)
{
    if (temp.length >= 2)
    {
        for (int i = 1; i <= temp.length - 1; i++)
        {
            int[] hold = temp[i];
            int[] holdP = temp[i-1];

            int j = i;

            while (j > 0 && hold[1] < holdP[1]) // 1 represents the reference of sorting
            {
                hold = temp[j];
                holdP = temp[j-1];

                temp[j] = holdP;
                temp[j-1] = hold;

                j--;
            }
        }
    }
}

 sortC(data);

I tried this one, but unfortunately it doesn't give a right sorting I couldn't figure out the pickle.

Answer 1

Use java.util.Arrays.sort with a custom Comparator.

int[][] temp = { { 1, 50, 5 }, { 2, 30, 8 }, { 3, 90, 6 },
        { 4, 20, 7 }, { 5, 80, 9 }, };
Arrays.sort(temp, new Comparator<int[]>() {
    @Override
    public int compare(int[] o1, int[] o2) {
        return Integer.compare(o2[1], o1[1]);
    }
});

As shmosel mentioned below, with Java 8, you can use:

Arrays.sort(temp, Comparator.comparingInt(arr -> arr[1]));

Answer 2

You can do this instead of writing your own sorting algorithm:

int[][] n = new int[10][];
//init your array here

List<int[]> ints = Arrays.asList(n);
Collections.sort(ints, new Comparator<int[]>() {
    @Override
    public int compare(int[] o1, int[] o2) {
        return o1[1] - o2[1]; // compare via second column
    }
});

and if you want make it array again:

int[][] result = ints.toArray(n);

Answer 3

Arrays.sort(boxTypes, (a, b) -> b[1] - a[1]);

or Using a priority queue

PriorityQueue<int[]> queue = new PriorityQueue<>((a, b)->b[1] - a[1]);