希尔排序的关键思想是使序列中任意间隔h的元素都是有序的，其中h是一个递增序列，使得该递增序列（如1/2 (3^k-1))递减（从N / 3开始递减到1），当h为1时，整个序列就是有序的了。简易实现及测试用例如下：

1 import java.util.logging.Handler; 2  3  4 public class Shell { 5  6     private static void exch(Comparable[] a, int i , int j){ 7         Comparable tmp = a[i]; 8         a[i] = a[j]; 9         a[j] = tmp;10     }11     12     private static boolean less(Comparable a, Comparable b)13     {14         return (a.compareTo(b) < 0);15     }16     17     private static void show(Comparable[] a)18     {19         int N = a.length;20         for(int i = 0; i < N; i++)21         {22             System.out.print(a[i] + " ");23         }24         System.out.println();25     }26     27     public static boolean isSorted(Comparable[] a)28     {29         int N = a.length;30         for(int i = 1; i < N; i++)31         {32             if(less(a[i], a[i - 1])) return false;33         }34         return true;35     }36     37     public static void sort(Comparable[] a)38     {39         int N = a.length;40         int h = 1;41         while(h < N / 3) h = 3 * h + 1;42         while(h >= 1)43         {44             for(int i = h; i < N; i++)45             {46                 for(int j = i; j >= h && less(a[j], a[j - h]); j -= h)47                     exch(a, j, j - h);48             }49             h = h / 3;50         }51     }52 53     public static void main(String[] args) {54         String[] a = StdIn.readAllStrings();55         Selection.sort(a);56         show(a);57     }58 }