別看3DES的程式碼很複雜，其實和DES程式碼一樣，核心程式碼就那麼幾行

加密部分的核心
Cipher cipher = Cipher.getInstance("DESede/ECB/PKCS5Padding");
cipher.init(Cipher.ENCRYPT_MODE, deskey);
return cipher.doFinal(data);

解密部分的核心
Cipher cipher = Cipher.getInstance("DESede/ECB/PKCS5Padding");
cipher.init(Cipher.DECRYPT_MODE,deskey);
return cipher.doFinal
 
(data);

完整程式碼

package DES;

import javax.crypto.Cipher;
import javax.crypto.SecretKey;
import javax.crypto.spec.SecretKeySpec;

public class ThreeDESUtil {

   //key 根據實際情況對應的修改
   private final byte[] keybyte="123456788765432112345678".getBytes(); //keybyte為加密金鑰，長度為24位元組
   private static final String Algorithm = "DESede"
 
; //定義 加密演算法,可用 DES,DESede,Blowfish
   private SecretKey deskey;
   //生成金鑰
   public ThreeDESUtil(){
       deskey = new SecretKeySpec(keybyte, Algorithm);
   }
   //加密
   public byte[] encrypt(byte[] data){
        try {
            Cipher cipher = Cipher.getInstance("DESede/ECB/PKCS5Padding");
            cipher.init(Cipher.ENCRYPT_MODE, deskey);
            return
 
 cipher.doFinal(data);
        } catch (Exception ex) {
            //加密失敗，打日誌
            ex.printStackTrace();
        } 
        return null;
   }
   //解密
   public byte[] decrypt(byte[] data){
       try {
            Cipher cipher = Cipher.getInstance("DESede/ECB/PKCS5Padding");
            cipher.init(Cipher.DECRYPT_MODE,deskey);
            return cipher.doFinal(data);
        } catch (Exception ex) {
            //解密失敗，打日誌
            ex.printStackTrace();
        } 
        return null;
   }

   public static void main(String[] args) throws Exception {
       ThreeDESUtil des=new ThreeDESUtil();
       String req ="cryptology";

       String toreq  = toHexString(req);
       System.err.println("十六進位制報文=="+toreq);
       byte[] srcData=req.toString().getBytes("utf-8");
       byte[] encryptData=des.encrypt(srcData);
       System.out.println("密文：");
       if(encryptData!=null){
           for(int i=0;i<encryptData.length;i++){
               String hex=Integer.toHexString(encryptData[i]);
               if(hex.length()>1)
                System.out.print(hex.substring(hex.length()-2)+" ");
               else
                System.out.print("0"+hex+" ");
           }
       }
       System.out.println("");
       System.out.println("明文："+req);
   }

   // 轉化字串為十六進位制編碼
   public static String toHexString(String s) {
       String str = "";
       for (int i = 0; i < s.length(); i++) {
           int ch = (int) s.charAt(i);
           String s4 = Integer.toHexString(ch);
           str = str + s4;
       }
       return str;
   }
}