MD5 加密解密 判断密码是否相等 全套实现方式

package com.mirai.comic.util.md5;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.io.UnsupportedEncodingException;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
/**
 * @Author:zzh @Email:zhangzihaopk@foxmail.com  @Time:2016/8/5
 */
public class MD5Util {
    protected static final Logger logger = LoggerFactory.getLogger(MD5Util.class);
    static MessageDigest messageDigest = null;
    /**
     * 判断新密码和旧密码是否正确  返回true 和 false
     *
     * @param newStr
     * @param oldMD5Str
     * @return
     */
    public final static boolean checkMD5(String newStr, String oldMD5Str) {
        String temp = encoderByMd5(newStr);
        return (temp != null && temp.equals(oldMD5Str)) ? true : false;
    }
    /**
     * 对给定的字符串进行加密
     *
     * @param source
     * @return 加密后的16进制的字符串
     */
    public final static String encoderByMd5(String source) {
        String tmp = source.substring(0, 1)
                + source.subSequence(source.length() - 1, source.length());
        tmp = md5(tmp);
        return md5(source + tmp);
    }
    private static String md5(String source) {
        if (logger.isDebugEnabled()) {
        }
        char hexDigits[] = {'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd',
                'e', 'f'};
        try {
            byte[] strTemp = source.getBytes();
            // 使用MD5创建MessageDigest对象
            MessageDigest mdTemp = MessageDigest.getInstance("MD5");
            mdTemp.update(strTemp);
            byte[] md = mdTemp.digest();
            int j = md.length;
            char str[] = new char[j * 2];
            int k = 0;
            for (int i = 0; i < j; i++) {
                byte b = md[i];
                str[k++] = hexDigits[b >> 4 & 0xf];
                str[k++] = hexDigits[b & 0xf];
            }
            if (logger.isDebugEnabled()) {
                logger.debug("加密后的字符串：" + new String(str));
            }
            return new String(str);
        } catch (Exception e) {
            logger.error("md5加密出错：" + source, e);
            return null;
        }
    }
    public static String encodeByMD5(String str) {
        try {
            if (messageDigest == null)
                messageDigest = MessageDigest.getInstance("MD5");
            messageDigest.reset();
            messageDigest.update(str.getBytes("UTF-8"));
        } catch (NoSuchAlgorithmException e) {
            logger.error("NoSuchAlgorithmException caught!", e);
        } catch (UnsupportedEncodingException e) {
            logger.error("UnsupportedEncodingException error!", e);
        }
        if (messageDigest == null)
            return "";
        byte[] byteArray = messageDigest.digest();
        StringBuffer md5StrBuff = new StringBuffer();
        for (int i = 0; i < byteArray.length; i++) {
            if (Integer.toHexString(0xFF & byteArray[i]).length() == 1)
                md5StrBuff.append("0").append(Integer.toHexString(0xFF & byteArray[i]));
            else
                md5StrBuff.append(Integer.toHexString(0xFF & byteArray[i]));
        }
        return md5StrBuff.toString();
    }
}