使用java.security.MessageDigest库的简单函数

public String stringMD5Hash(String text) throws NoSuchAlgorithmException {
    MessageDigest messageDigest = MessageDigest.getInstance("MD5");
    byte[] bytes = messageDigest.digest(text.getBytes());
    StringJoiner stringJoiner = new StringJoiner("");
    for (byte b : bytes) {
        stringJoiner.add(Integer.toHexString((b & 0xFF) | 0x100).substring(1, 3));
    }
    return stringJoiner.toString();
}

对于文件使用这个函数

public static String FileMD5Hash(File file) throws NoSuchAlgorithmException, IOException {
    MessageDigest messageDigest = MessageDigest.getInstance("MD5");
    byte[] bytes = messageDigest.digest(getFileBytes(file));
    StringJoiner stringJoiner = new StringJoiner("");
    for (byte b : bytes) {
        stringJoiner.add(Integer.toHexString((b & 0xFF) | 0x100).substring(1, 3));
    }
    return stringJoiner.toString();
}

public static byte[] getFileBytes(File file) throws IOException{
    InputStream inputStream = new FileInputStream(file);
    ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
    byte[] bytes = new byte[1024];
    int bytesRead;
    while ((bytesRead = inputStream.read(bytes)) != -1) {
        byteArrayOutputStream.write(bytes, 0, bytesRead);
    }
    return byteArrayOutputStream.toByteArray();
}

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 "";
    }
}

如果你真的想要返回一个字符串，而不是字节数组，你总是可以这样做:

String plaintext = "your text here";
MessageDigest m = MessageDigest.getInstance("MD5");
m.reset();
m.update(plaintext.getBytes());
byte[] digest = m.digest();
BigInteger bigInt = new BigInteger(1,digest);
String hashtext = bigInt.toString(16);
// Now we need to zero pad it if you actually want the full 32 chars.
while(hashtext.length() < 32 ){
  hashtext = "0"+hashtext;
}

无论如何，我无意中发现了这一点，因为我想从一个将安装COM组件的程序的自然键合成guid;我希望进行综合，以免管理GUID生命周期。我将使用MD5，然后使用UUID类从中获取一个字符串。(http://stackoverflow.com/questions/2190890/how-can-i-generate-guid-for-a-string-values/12867439提出了这个问题)。

在任何情况下，java.util.UUID都可以从MD5字节中获得一个漂亮的String。

return UUID.nameUUIDFromBytes(md5Bytes).toString();

import java.security.MessageDigest

val digest = MessageDigest.getInstance("MD5")

//Quick MD5 of text
val text = "MD5 this text!"
val md5hash1 = digest.digest(text.getBytes).map("%02x".format(_)).mkString

//MD5 of text with updates
digest.update("MD5 ".getBytes())
digest.update("this ".getBytes())
digest.update("text!".getBytes())
val md5hash2 = digest.digest().map(0xFF & _).map("%02x".format(_)).mkString

//Output
println(md5hash1 + " should be the same as " + md5hash2)