Java中数字黑洞实现代码

import java.util.Arrays; 
import java.util.Scanner; 
public class Main { 
  public static void main(String args[]) { 
    Scanner sc = new Scanner(System.in); 
    int x = sc.nextInt(); 
    int ans = ds(x)-xs(x); 
    if(ans==0){ 
      System.out.printf("%04d - %04d = %04d\n",ds(x),xs(x),ans); 
    }else{ 
      int n ; 
      do{ 
        n = ds(x)-xs(x); 
        System.out.printf("%04d - %04d = %04d\n",ds(x),xs(x),n); 
        x = n; 
      }while(n!=6174); 
    } 
  } 
  public static int ds (int x){ 
    int[]a = new int[4]; 
    a[0] = x/1000; 
    a[1] = x/100%10; 
    a[2] = x/10%10; 
    a[3] = x%10; 
    Arrays.sort(a); 
    int sum = a[3]*1000+a[2]*100+a[1]*10+a[0]; 
    return sum; 
  } 
  public static int xs (int x){ 
    int[]a = new int[4]; 
    a[0] = x/1000; 
    a[1] = x/100%10; 
    a[2] = x/10%10; 
    a[3] = x%10; 
    Arrays.sort(a); 
    int sum = a[0]*1000+a[1]*100+a[2]*10+a[3]; 
    return sum; 
  } 
} 

4695
9654 - 4569 = 5085
8550 - 0558 = 7992
9972 - 2799 = 7173
7731 - 1377 = 6354
6543 - 3456 = 3087
8730 - 0378 = 8352
8532 - 2358 = 6174