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Dahua ICC Open API SDK for Java

There is a newer version: 1.0.13.10

package com.dahuatech.hutool.core.codec;

/**
 * 凯撒密码实现

 * 算法来自：https://github.com/zhaorenjie110/SymmetricEncryptionAndDecryption
 *
 * @author looly
 */
public class Caesar {

  // 26个字母表
  public static String table = "AaBbCcDdEeFfGgHhIiJjKkLlMmNnOoPpQqRrSsTtUuVvWwXxYyZz";

  /**
   * 传入明文，加密得到密文
   *
   * @param message 加密的消息
   * @param offset 偏移量
   * @return 加密后的内容
   */
  public static String encode(String message, int offset) {
    final int len = message.length();
    final char[] plain = message.toCharArray();
    char c;
    for (int i = 0; i < len; i++) {
      c = message.charAt(i);
      if (false == Character.isLetter(c)) {
        continue;
      }
      plain[i] = encodeChar(c, offset);
    }
    return new String(plain);
  }

  /**
   * 传入明文解密到密文
   *
   * @param cipherText 密文
   * @param offset 偏移量
   * @return 解密后的内容
   */
  public static String decode(String cipherText, int offset) {
    final int len = cipherText.length();
    final char[] plain = cipherText.toCharArray();
    char c;
    for (int i = 0; i < len; i++) {
      c = cipherText.charAt(i);
      if (false == Character.isLetter(c)) {
        continue;
      }
      plain[i] = decodeChar(c, offset);
    }
    return new String(plain);
  }

  // -----------------------------------------------------------------------------------------
  // Private method start

  /**
   * 加密轮盘
   *
   * @param c 被加密字符
   * @param offset 偏移量
   * @return 加密后的字符
   */
  private static char encodeChar(char c, int offset) {
    int position = (table.indexOf(c) + offset) % 52;
    return table.charAt(position);
  }

  /**
   * 解密轮盘
   *
   * @param c 字符
   * @return 解密后的字符
   */
  private static char decodeChar(char c, int offset) {
    int position = (table.indexOf(c) - offset) % 52;
    if (position < 0) {
      position += 52;
    }
    return table.charAt(position);
  }
  // -----------------------------------------------------------------------------------------
  // Private method end
}