How can I generate an MD5 hash in Java?

Question

Is there any method to generate MD5 hash of a string in Java?

Answer 1

The MessageDigest class can provide you with an instance of the MD5 digest.

When working with strings and the crypto classes be sure to always specify the encoding you want the byte representation in. If you just use string.getBytes() it will use the platform default. (Not all platforms use the same defaults)

import java.security.*;

..

byte[] bytesOfMessage = yourString.getBytes("UTF-8");

MessageDigest md = MessageDigest.getInstance("MD5");
byte[] theMD5digest = md.digest(bytesOfMessage);

If you have a lot of data take a look at the .update(xxx) methods which can be called repeatedly. Then call .digest() to obtain the resulting hash.

Answer 2

You need java.security.MessageDigest.

Call MessageDigest.getInstance("MD5") to get a MD5 instance of MessageDigest you can use.

The compute the hash by doing one of:

• Feed the entire input as a byte[] and calculate the hash in one operation with md.digest(bytes).
• Feed the MessageDigest one byte[] chunk at a time by calling md.update(bytes). When you're done adding input bytes, calculate the hash with md.digest().

The byte[] returned by md.digest() is the MD5 hash.