Shell sort java program

Shellsort: which increment sequence to use? Powers of two. 1, 2, 4, 8, 16, 32, ... No. Powers of two minus one. 1, 3, 7, 15, 31, 63, … Maybe. 3x + 1. 1, 4, 13, 40, 121, 364, … OK. Easy to compute.

class ShellSort {
    public static void sort(int[] array) {
        int N = array.length;
        
        int h = 1;
        while(h < N/3) {
            // 3h +1 sequence 
            h = 3*h+1; // 1, 4, 13, 40, 121, 364, ...
        }
        
        while(h >=1) { // h-sort the array.
            // insertion sort
            for(int i = h; i < N; i++) {
                for(int j = i; j >= h && less(array[j], array[j-h]); j -= h) {
                    swap(array, j, j-h);
                }
            }
            h = h/3; // move to next increment
        }
    }
    
    private static void swap(int[] array, int i, int j) {
        int temp = array[i];
        array[i] = array[j];
        array[j] = temp;
    }
    
    private static boolean less(int key1, int key2) {
        return key1 < key2;
    }
    
    private static void display(int[] array) {
        for(int key : array) {
            System.out.print(key + " ");
        }
    }
    
	public static void main (String[] args) {
		int[] array = new int[] {11,13,7,12,16,9,24,5,10,3};
		System.out.println("Unsorted array : ");
		display(array);
		
		sort(array);
		System.out.println("\nSorted array : ");
		display(array);
	}
}

Unsorted array : 
11 13 7 12 16 9 24 5 10 3 
Sorted array : 
3 5 7 9 10 11 12 13 16 24