PasswordGenerator.java

package de.fhb.autobday.commons;

/**
 * This class generates passwords and signs for security affairs.
 *
 *
 * @author Tino Reuschel mail: reuschel@fh-brandenburg.de
 * @author Michael Koppen mail: koppen@fh-brandenburg.de 
 * @author Andy Klay mail: klay@fh-brandenburg.de
 *
 */
public class PasswordGenerator {

	/**
	 * Mode for generating a random sequence of numbers and letters
	 */
	public final static int MODE_BOTH = 0;
	/**
	 * Mode for generating a random sequence of numbers
	 */
	public final static int MODE_ONLY_NUMERIC = 1;
	/**
	 * Mode for generating a random sequence of letters
	 */
	public final static int MODE_ONLY_LETTERS = 2;
	/**
	 * password length
	 */
	public final static int PASSWORD_LENGTH = 8;
	/**
	 * salt length
	 */
	public final static int SALT_LENGTH = 5;

	/**
	 * generate a random password consists of lowercase letters and uppercase
	 * letters
	 *
	 * @return String - password
	 */
	public static String generatePassword() {

		return generateSigns(PASSWORD_LENGTH, MODE_ONLY_LETTERS);
	}

	/**
	 * generate a random sequence of char numbers
	 *
	 * @return String - numbers
	 */
	public static String generateNumbers() {

		return generateSigns(SALT_LENGTH, MODE_ONLY_NUMERIC);
	}

	/**
	 * generate a random salt consists of lowercase letters and uppercase
	 * letters and numbers
	 *
	 * @return String - salt
	 */
	public static String generateSalt() {

		return generateSigns(SALT_LENGTH, MODE_BOTH);
	}

	/**
	 * generate a random sequence of numbers or letters or both
	 *
	 * @param int length
	 * @param int generationMode
	 * @return String - random char sequence
	 */
	private static String generateSigns(int length, int generationMode) {

		final int ALPHABET_LENGTH = 26;
		final int NUMERIC_LENGTH = 10;
		final int ASCII_LOWERLETTER_OFFSET = 97;
		final int ASCII_UPPERLETTER_OFFSET = 65;
		final int ASCII_NUMBER_OFFSET = 48;

		StringBuilder generateContent = new StringBuilder();

		//generating
		switch (generationMode) {
			case MODE_BOTH:

				// generate letters and numbers
				for (int x = 0; x < length; x++) {
					//letter or number?
					if (Math.round(Math.random()) == 0) {
						//letter
						//upper or lower case letter?
						if (Math.round(Math.random()) == 0) {
							//lower case
							generateContent.append((char) ((int) (Math.random() * ALPHABET_LENGTH) + ASCII_LOWERLETTER_OFFSET));
						} else {
							//upper case
							generateContent.append((char) ((int) (Math.random() * ALPHABET_LENGTH) + ASCII_UPPERLETTER_OFFSET));
						}
					} else {
						//number
						generateContent.append((char) ((int) (Math.random() * NUMERIC_LENGTH) + ASCII_NUMBER_OFFSET));
					}
				}

				break;

			case MODE_ONLY_NUMERIC:
				;

				//generate only numbers
				for (int x = 0; x < length; x++) {
					generateContent.append((char) ((int) (Math.random() * NUMERIC_LENGTH) + ASCII_NUMBER_OFFSET));
				}

				break;
			case MODE_ONLY_LETTERS:

				//generate only letters
				for (int x = 0; x < length; x++) {
					if (Math.round(Math.random()) == 0) {
						generateContent.append((char) ((int) (Math.random() * ALPHABET_LENGTH) + ASCII_LOWERLETTER_OFFSET));
					} else {
						generateContent.append((char) ((int) (Math.random() * ALPHABET_LENGTH) + ASCII_UPPERLETTER_OFFSET));
					}
				}

				break;
		}

		return generateContent.toString();
	}
}