Generate MD5 digest in Java

MD5.java

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

public class MD5 {
	
	private static final char[] hexCode = "0123456789abcdef".toCharArray();
	
	private static String toHexString(byte[] data) {
		if (data == null) {
			return null;
		}
		StringBuilder r = new StringBuilder(data.length * 2);
		for (byte b : data) {
			r.append(hexCode[(b >> 4) & 0xF]);
			r.append(hexCode[(b & 0xF)]);
		}
		return r.toString();
	}
	
	public static String md5HexString(String param) {
		MessageDigest algorithm;
		try {
			algorithm = MessageDigest.getInstance("MD5");
		} catch (NoSuchAlgorithmException e) {
			throw new RuntimeException(e);
		}
		algorithm.reset();
		algorithm.update(param.getBytes());
		byte[] messageDigest = algorithm.digest();
		return toHexString(messageDigest);
	}

	public static void main(String[] args) {
		System.out.println(MD5.md5HexString("123456"));
	}

}