using Java to get a file's md5 checksum?

MessageDigest md = MessageDigest.getInstance("MD5");
InputStream is = new FileInputStream("file.txt");
try {
  is = new DigestInputStream(is, md);
  // read stream to EOF as normal...
}
finally {
  is.close();
}
byte[] digest = md.digest();

FileInputStream fis = new FileInputStream( new File("foo" ) );
String md5 = org.apache.commons.codec.digest.DigestUtils.md5Hex( fis );

try {
   String s = "TEST STRING";
   MessageDigest md5 = MessageDigest.getInstance("MD5");
   md5.update(s.getBytes(),0,s.length());
   String signature = new BigInteger(1,md5.digest()).toString(16);
   System.out.println("Signature: "+signature);

} catch (final NoSuchAlgorithmException e) {
   e.printStackTrace();
}

File myfile = new File("myfile.txt");
long checksum = Files.getChecksum(myfile , new java.util.zip.CRC32());

File myfile = new File("myfile.txt");
byte[] digest = Files.getDigest(myfile , MessageDigest.getInstance("SHA-256"));

public static String MD5Hash(String toHash) throws RuntimeException {
   try{
       return String.format("%032x", // produces lower case 32 char wide hexa left-padded with 0
      new BigInteger(1, // handles large POSITIVE numbers
           MessageDigest.getInstance("MD5").digest(toHash.getBytes())));
   }
   catch (NoSuchAlgorithmException e) {
      // do whatever seems relevant
   }
}

...
String signature = new BigInteger(1,md5.digest()).toString(16);
...

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

<checksum file="${jarFile}" todir="${toDir}"/>