123456所有排列組合

  String str = "123456";
  char[] arr1 = str.toCharArray();
  char[] arr2 = Arrays.copyOf(arr1,arr1.length);
  for(int i=0;i<arr1.length-1;i++){
     for(int j = i+1;j<arr2.length;j++){
          System.out.println(arr1[i] + "," + arr2[j]);
     }
  }