Java sort comparator to sort array

/**
 * @author lautturi.com 
 * Java example: sort comparator for 2d array in java
 */

import java.util.*;

public class Lautturi {
	public static void main(String[] args) {
		int[][] arr2d = {{3, 2},{1,4},{6,7},{5,9},{8,12}};

		System.out.println(Arrays.deepToString(arr2d));
		
		// sort a 2D-array in java
		Arrays.sort(arr2d, (int[] o1, int[] o2) -> o1[0] - o2[0]);

		System.out.println(Arrays.deepToString(arr2d));
	}
}

output:

[[3, 2], [1, 4], [6, 7], [5, 9], [8, 12]]
[[1, 4], [3, 2], [5, 9], [6, 7], [8, 12]]