PasswordGenerator.java

/*
 * Copyright 2001-2013 Geert Bevin (gbevin[remove] at uwyn dot com)
 * Licensed under the Apache License, Version 2.0 (the "License")
 */
package com.uwyn.rife.tools;

import java.util.Random;

public abstract class PasswordGenerator
{
    public static final int DIGITS_ONLY = 0;
    public static final int LETTERS_ONLY = 1;
    public static final int MIXED = 2;
    private static final String LETTERS = "qwertyuiopzxcvbnmasdfghjklAZERTYUIOPMLKJHGFDSQWXCVBN";
    private static final int LETTERS_LENGTH = LETTERS.length();
    private static final String NUMBERS = "1357924680";
    private static final int NUMBERS_LENGTH = NUMBERS.length();

    public static String get(int length)
    {
        return get(new Random(System.currentTimeMillis()), length, MIXED);
    }

    public static String get(int length, int type)
    {
        return get(new Random(System.currentTimeMillis()), length, type);
    }

    public static String get(Random random, int length, int type)
    {
        if (length <= 0) throw new IllegalArgumentException("length has to be bigger zero");
        if (type != DIGITS_ONLY &&
            type != LETTERS_ONLY &&
            type != MIXED)
        {
            throw new IllegalArgumentException("invalid type");
        }

        StringBuilder generated_password = new StringBuilder("");
        boolean type_selector;

        for (int i = 0; i < length; i++)
        {
            type_selector = random.nextBoolean();

            // characters
            if (LETTERS_ONLY == type ||
                type != DIGITS_ONLY && type_selector)
            {
                char c = LETTERS.charAt((int)((double)LETTERS_LENGTH * random.nextDouble()));
                if (random.nextDouble() > 0.5D)
                {
                    c = Character.toUpperCase(c);
                }
                generated_password.append(c);
            }
            // digits
            else
            {
                generated_password.append(NUMBERS.charAt((int)((double)NUMBERS_LENGTH * random.nextDouble())));
            }
        }

        return generated_password.toString();
    }
}