Transform any string to MD5 hash and then to HEX representation. Useful for file names.

Util.java

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

public class Util {
    private static char[] hex = {'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F'};

    /**
     * Transform any string to MD5 hash and then to HEX representation.
     * Very useful for using strings as file names, like when the string
     * is a url or another arbitrary string.
     * 
     * @param text
     * @return
     */
    public String md5(String text) {
        MessageDigest hasher;

        try {
            hasher = MessageDigest.getInstance("MD5");
        } catch (NoSuchAlgorithmException e) {
            e.printStackTrace();
            return null;
        }

        hasher.update(text.getBytes());
        byte bytes[] = hasher.digest();

        char[] result = new char[bytes.length * 2];
        for(int i = 0; i < bytes.length; ++i) {
            result[i << 2] = hex[bytes[i] >> 4];
            result[(i << 2) + 1] = hex[0x0F & bytes[i]];
        }

        return new String(result);
    }
}