DES加密中文乱码问题

为什么我无论怎么换编码方式，中文的明文在解码之后始终是乱码呢

package com.ky.controller.test.md5;
 
import java.io.IOException;
 
import javax.crypto.Cipher;
import javax.crypto.spec.SecretKeySpec;
 
import sun.misc.BASE64Encoder;
import sun.misc.BASE64Decoder;
 
/**
 * @author Luyong
 */
public class DESSecretUtil {
 
    /**
     * 使用DES对字符串加密
     * 
     * @param str
     *            utf8编码的字符串
     * @param key
     *            密钥（56位，7字节）
     * 
     */
    public static byte[] desEncrypt(String str, String key) throws Exception {
        if (str == null || key == null)
            return null;
        Cipher cipher = Cipher.getInstance("DES/ECB/PKCS5Padding");
        cipher.init(Cipher.ENCRYPT_MODE, new SecretKeySpec(key.getBytes("utf-8"), "DES"));
        byte[] bytes = cipher.doFinal(str.getBytes("utf-8"));
        return bytes;
    }
 
    /**
     * 使用DES对数据解密
     * 
     * @param bytes
     *            utf8编码的二进制数据
     * @param key
     *            密钥（16字节）
     * @return 解密结果
     * @throws Exception
     */
    public static String desDecrypt(byte[] bytes, String key) throws Exception {
        if (bytes == null || key == null)
            return null;
        Cipher cipher = Cipher.getInstance("DES/ECB/PKCS5Padding");
        cipher.init(Cipher.DECRYPT_MODE, new SecretKeySpec(key.getBytes("utf-8"), "DES"));
        bytes = cipher.doFinal(bytes);
        return new String(bytes, "utf-8");
    }
 
    /**
     * 使用base64解决乱码
     * 
     * @param secretKey
     *            加密后的字节码
     */
    public static String jdkBase64String(byte[] secretKey) {
        BASE64Encoder encoder = new BASE64Encoder();
        return encoder.encode(secretKey);
    }
 
    /**
     * 使用jdk的base64 解密字符串 返回为null表示解密失败
     * 
     * @throws IOException
     */
    public static byte[] jdkBase64Decoder(String str) throws IOException {
        BASE64Decoder decoder = new BASE64Decoder();
        return decoder.decodeBuffer(str);
    }
 
    public static void main(String[] args) throws Exception {
 
        String openId = "sdn_" + jdkBase64String(desEncrypt("DDOS_7", "sdn_ddos"));
        System.out.println(openId);
 
        String s = openId.replace("sdn_", "");
        String desDecrypt = desDecrypt(jdkBase64Decoder(s), "sdn_ddos");
        System.out.println(desDecrypt);
    }
 
}

mchar 中的本来就是乱码