MD5Utils

public class MD5Utils {

    private static final String hexDigIts[] = {"0","1","2","3","4","5","6","7","8","9","a","b","c","d","e","f"};

    /**
     * MD5加密
     * @param origin 字符
     * @param charsetname 编码
     * @return
     */
    public static String MD5Encode(String origin, String charsetname){
        String resultString = null;
        try{
            resultString = new String(origin);
            //创建具有MD5算法的信息摘要
            MessageDigest md = MessageDigest.getInstance("MD5");
            if(null == charsetname || "".equals(charsetname)){
            //使用指定的字节数组对摘要进行最后更新，然后完成摘要计算
            //将得到的字节数组变成字符串返回
                resultString = byteArrayToHexString(md.digest(resultString.getBytes()));
            }else{
                resultString = byteArrayToHexString(md.digest(resultString.getBytes(charsetname)));
            }
        }catch (Exception e){
        }
        return resultString;
    }

        /**
     * 将字节数组转换成十六进制，并以字符串的形式返回
     * 128位是指二进制位。二进制太长，所以一般都改写成16进制，
     * 每一位16进制数可以代替4位二进制数，所以128位二进制数写成16进制就变成了128/4=32位。
     */
    public static String byteArrayToHexString(byte b[]){
        StringBuffer resultSb = new StringBuffer();
        for(int i = 0; i < b.length; i++){
            resultSb.append(byteToHexString(b[i]));
        }
        return resultSb.toString();
    }
    /**
     * 将一个字节转换成十六进制，并以字符串的形式返回
     */
    public static String byteToHexString(byte b){
        int n = b;
        if(n < 0){
            n += 256;
        }
        int d1 = n / 16;
        int d2 = n % 16;
        return hexDigIts[d1] + hexDigIts[d2];
    }

}        

String md5Str = MD5Utils.MD5Encode("123456","utf8");