我的回答不是很直白:

private String md5(String s) {
    try {
        MessageDigest m = MessageDigest.getInstance("MD5");
        m.update(s.getBytes(), 0, s.length());
        BigInteger i = new BigInteger(1,m.digest());
        return String.format("%1$032x", i);         
    } catch (NoSuchAlgorithmException e) {
        e.printStackTrace();
    }
    return null;
}

另一种实现:Java中的快速MD5实现

String hash = MD5.asHex(MD5.getHash(new File(filename)));

试试这个:

public static String getHashMD5(String string) {
    try {
        MessageDigest md = MessageDigest.getInstance("MD5");
        BigInteger bi = new BigInteger(1, md.digest(string.getBytes()));
        return bi.toString(16);
    } catch (NoSuchAlgorithmException ex) {
        Logger.getLogger(MD5Utils.class
                .getName()).log(Level.SEVERE, null, ex);

        return "";
    }
}

这就是我来这里的目的-一个方便的scala函数，返回MD5哈希字符串:

def md5(text: String) : String = java.security.MessageDigest.getInstance("MD5").digest(text.getBytes()).map(0xFF & _).map { "%02x".format(_) }.foldLeft(""){_ + _}

下面是我如何使用它:

final MessageDigest messageDigest = MessageDigest.getInstance("MD5");
messageDigest.reset();
messageDigest.update(string.getBytes(Charset.forName("UTF8")));
final byte[] resultByte = messageDigest.digest();
final String result = new String(Hex.encodeHex(resultByte));

来自Apache Commons项目的Hex。

另一个实现:

import javax.xml.bind.DatatypeConverter;

String hash = DatatypeConverter.printHexBinary( 
           MessageDigest.getInstance("MD5").digest("SOMESTRING".getBytes("UTF-8")));