MD5加密工具类--加密byte数组或字符串

Java版的加密byte数组在网上很难搜索出来。。

import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

public class MD5Util {
    private static char hexDigits[] = {'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f'};
    private static MessageDigest messagedigest = null;

    /**
     * MessageDigest初始化
     */
    static {
        try {
            messagedigest = MessageDigest.getInstance("MD5");
        } catch (NoSuchAlgorithmException e) {
            System.err.println("MD5FileUtil messagedigest初始化失败");
            e.printStackTrace();
        }
    }

    /**
     * 对字符串进行MD5加密
     */
    public static String getMD5String(String s) {
        return getMD5String(s.getBytes());
    }

    /**
     * 对byte类型的数组进行MD5加密
     */
    public static String getMD5String(byte[] bytes) {
        messagedigest.update(bytes);
        return bufferToHex(messagedigest.digest());
    }

    private static String bufferToHex(byte bytes[]) {
        return bufferToHex(bytes, 0, bytes.length);
    }

    private static String bufferToHex(byte bytes[], int m, int n) {
        StringBuilder stringbuffer = new StringBuilder(2 * n);
        int k = m + n;
        for (int l = m; l < k; l++) {
            char c0 = hexDigits[(bytes[l] & 0xf0) >> 4];
            char c1 = hexDigits[bytes[l] & 0xf];
            stringbuffer.append(c0);
            stringbuffer.append(c1);
        }
        return stringbuffer.toString();
    }
}