MD5Checksum.java

package com.holo.actions;

import java.io.*;
import java.security.MessageDigest;

public class MD5Checksum {

	public static byte[] createChecksum(File file) throws Exception {

		// TODO check to see if file exists
		String filename = file.getAbsolutePath();
		InputStream fis = new FileInputStream(filename);

		byte[] buffer = new byte[1024];
		MessageDigest complete = MessageDigest.getInstance("MD5");
		int numRead;
		do {
			numRead = fis.read(buffer);
			if (numRead > 0) {
				complete.update(buffer, 0, numRead);
			}
		} while (numRead != -1);
		fis.close();
		return complete.digest();
	}

	// see this How-to for a faster way to convert
	// a byte array to a HEX string
	public static String getMD5Checksum(File file) throws Exception {
		byte[] b = createChecksum(file);
		String result = "";
		for (int i = 0; i < b.length; i++) {
			result += Integer.toString((b[i] & 0xff) + 0x100, 16).substring(1);
		}
		return result;
	}
}