加密、解密

凯撒加密：

  public static void main(String[] args) {
    String input="hello world";
    //向右移动
    int key =3;

    //转换字节数组
      char[] chars=input.toCharArray();
      //装密文
      StringBuilder sb = new StringBuilder();
      for (char c :chars ) {
          int d=c;
          d = d+key;
          char newd= (char) d;
          sb.append(newd);

      }
    System.out.println("密文："+sb.toString());

      //反转
      StringBuilder bs = new StringBuilder();
      String output =sb.toString();
      char[] outchars=output.toCharArray();
      for (char c : outchars) {
          int d=c;
          d= d-key;
          char newd= (char) d;
          bs.append(newd);

      }
    System.out.println("明文：" + bs.toString());
  }