How can we sort both row-wise ascending and column-wise descending of 2D arrays in Java?

Question

I would like to sort a 2D array both row wise and column wise in Java. Is there a way to do that similar to following python code. I have array as numbers[][2];

python code

# it first sorts based on index 0; if they match, it reverse sort based on index 1
numbers.sort(key: lambda x:(x[0], -x[1])) 

Can we achieve the same in Java through Arrays.sort(), if yes, what will be the comparator that I need to pass ?

Answer 1

You can use the following code:

Arrays.sort(
    numbers, 
    Comparator.comparing((int[] x) -> x[0])
              .thenComparing(
                  (int[] x) -> x[1], 
                  Comparator.<Integer>naturalOrder().reversed()));

This uses the overload of Arrays.sort that receives a Comparator .

Maybe using a plain lambda expression is better:

Arrays.sort(
    numbers, 
    (a, b) -> a[0] < b[0] ? -1 : a[0] > b[0] ?  1 :
              a[1] < b[1] ?  1 : a[1] > b[1] ? -1 : 0);