RandomUtil.java Source code

Introduction

Here is the source code for RandomUtil.java

Source

//package org.boticelli.util;

import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;
import java.util.Arrays;

//import org.apache.log4j.Logger;

public class RandomUtil {
    //  protected static Logger log = Logger.getLogger(RandomUtil.class);

    private static String[] secureRndNames = new String[] { System.getProperty("boticelli.securerandom"),
            "SHA1PRNG", "IBMSecureRandom" };

    private RandomUtil() {

    }

    /**
     * Creates a new secure random number generator. The following secure random
     * algorithm names are tried:
     * <ul>
     * <li>The value of system property "boticelli.securerandom", if set. </li>
     * <li> "SHA1PRNG" </li>
     * <li> "IBMSecureRandom" (available if running in the IBM JRE) </li>
     * </ul>
     */
    private static SecureRandom createSecureRandom() {
        SecureRandom secureRnd = null;
        try {

            for (int i = 0; i < secureRndNames.length; i++) {
                try {
                    if (secureRndNames[i] != null) {
                        secureRnd = SecureRandom.getInstance(secureRndNames[i]);
                        break;
                    }
                } catch (NoSuchAlgorithmException nsae) {
                    //  log.debug("no secure random algorithm named \"" + secureRndNames[i] + "\"",
                    //      nsae);
                }
            }
            if (secureRnd == null) {
                throw new IllegalStateException(
                        "no secure random algorithm found. (tried " + Arrays.asList(secureRndNames) + ")");
            }
            secureRnd.setSeed(System.currentTimeMillis());
        } catch (Exception e) {
            // log.fatal("error initializing secure random", e);
        }

        return secureRnd;
    }

    /**
     * Generates a secure random word with the given length consisting of
     * uppercase and lowercase letters and numbers.
     * 
     * @param len Amount of random characters to generate
     * @return random Word containing letters and numbers.
     */
    public static String createWord(int len) {
        return createWord(len, null);
    }

    /**
     * Generates a secure random word with the given length.
     * 
     * @param len Amount of random characters to generate
     * @param alphabet Alphabet to generate from.
     * @return random Word containing letters and numbers.
     */
    public static String createWord(int len, char[] alphabet) {
        SecureRandom random = createSecureRandom();

        if (alphabet == null) {
            alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz1234567890".toCharArray();
        }

        StringBuffer out = new StringBuffer(len);
        for (int i = 0; i < len; i++) {
            out.append(alphabet[random.nextInt(alphabet.length)]);
        }

        return out.toString();
    }
}