凯撒密码解密字符串。

Question

利用map，使用凯撒密码（k=3）将字符串“trphzdvqrw exlowlqdgdb.”进行解密，结果错误。

Answer 1

package com.test.kaisamima;

import java.util.HashMap;
import java.util.Map;

/**

• 凯撒密码

• @date 2022/04/06

• /
  public class Kaisamima {
  private static final String str = "abcdefghijklmnopqrstuvwxyz";

  public static void main(String[] args) {

    // TODO Auto-generated method stub
    Map<Character, Character> map = init(3);
    String s = "trphzdvqrw exlowlqdgdb.";
    char[] ss = s.toCharArray();
    StringBuffer sb = new StringBuffer();
    for (char c : ss) {
        Character cc = map.get(c);
        if (cc == null) {
            cc = c;
        }
        sb.append(cc);
    }
    System.out.println(sb + "===========");
  

  }

  private static Map<Character, Character> init(int k) {

    Map<Character, Character> map = new HashMap<Character, Character>();
    char strs[] = str.toCharArray();
    for (char c : strs) {
        int i = str.indexOf(c);
        int index = i + k;
        if (index >= strs.length) {
            index = index % strs.length;
        }
        map.put(c, strs[index]);
    }
    return map;
  

  }
  }