java实现置换密码加密解密

import java.util.Scanner;

public class replacement {


 public static void main(String[] args) {
  Scanner sc = new Scanner(System.in);
  System.out.println("请输入带加密的明文：");
  String plaintexts = sc.nextLine();
  int len = plaintexts.length() % 7 == 0 ? plaintexts.length() / 7 : (plaintexts.length() / 7) + 1;//定义二维数组是要用到，主要作用是确定二维数组中一维数组的个数
  char[] plaintext_char = new char[7 * len];//先将明文存入一维数组中，在后面再将其存入二维数组中
  char[][] arr = new char[len][7];//存放明文和解密后的明文的二维数组
  char[][] miwen = new char[len][7];//存放密文的二维数组
  char[] n=new char[7];//在解密过程中用来消掉多余的填充的0
  int[] key = {6, 3, 0, 4, 1, 5, 2};//加密秘钥
  int[] transkey = {2, 4, 6, 1, 3, 5, 0};//解密秘钥

  fill(plaintexts, plaintext_char, len, arr);
  encryption(len, miwen, arr, key);
  System.out.println("加密后的明文是：");
  for (int i = 0; i < len; i++) {
   for (int j = 0; j < miwen[i].length; j++) {
    System.out.print(miwen[i][j]);
   }
  }//输出密文
  System.out.println(" ");
  System.out.println("按下1解密或按其他任意键退出：");
  String a=sc.nextLine();
  if (a.equals("1")){
   decryption(n,len, miwen, arr, transkey,plaintexts);
   for (int i = 0; i < len; i++) {
    for (int j = 0; j < arr[i].length; j++) {
     System.out.print(arr[i][j]);
    }
   }
  }else {
   System.out.println("退出！");
  }//输出明文或退出
 }

 public static void fill(String plaintexts, char[] plaintext_char, int len, char[][] arr) {
  for (int i = 0; i < plaintexts.length(); i++) {
   plaintext_char[i] = plaintexts.charAt(i);
  }//将输入的字符串存入扩充好的一维数组中，此时数组长度已达到标准，但是多出来的填充为是'\0'
  for (int i = 0; i < plaintext_char.length; i++) {
   if (plaintext_char[i] == '\u0000') {
    plaintext_char[i] = '0';
   }//将字符串数组中的空字符'\0'替换为0
 for (int i = 0; i < len; i++) {
   for (int j = i * 7, k = 0; j < 7 * (i + 1) && k < 7; j++, k++) {
    arr[i][k] = plaintext_char[j];
   }
  }//将扩充后的明文存入二维数组中，每七个一个一维数组
 }

 public static void encryption(int len, char[][] miwen, char[][] arr, int[] key) {
  for (int i = 0; i < len; i++) {
   for (int j = 0; j < 7; j++) {
    miwen[i][j] = arr[i][key[j]];
   }
  }
 }//加密方法
 public static void decryption(char[] n,int len, char[][] miwen, char[][] arr, int[] trankey,String plaintexts) {
  for (int i = 0; i < len; i++) {
   for (int j = 0; j < 7; j++) {
    arr[i][j] = miwen[i][trankey[j]];
   }
  }
  for (int i = 0; i <7-(7*len-plaintexts.length()); i++) {
   n[i]=arr[arr.length-1][i];
  }//7-(7*len-plaintexts.length())是二维数组中最后一个一维数组中的非填充位的个数，将非填充位加到n中
  arr[len-1]=n;//用n取代二维数组中最后一个数组，相当于将填充的0消去
 }//解密方法
}