randomstring.java

Jive Forums 1.0 src

/**
 * RandomString.java
 * Bill Lynch
 * CoolServlets.com
 * March 26, 1999
 * Version 1.0
 *
 *    Copyright (C) 1999  Bill Lynch
 *
 *    This program is free software; you can redistribute it and/or modify
 *    it under the terms of the GNU General Public License as published by
 *    the Free Software Foundation; either version 2 of the License, or
 *    (at your option) any later version.
 *
 *    This program is distributed in the hope that it will be useful,
 *    but WITHOUT ANY WARRANTY; without even the implied warranty of
 *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *    GNU General Public License for more details.
 *
 *    You should have received a copy of the GNU General Public License
 *    along with this program; if not, write to the Free Software
 *    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

package com.coolservlets.util;

/**
 * A class that generates random strings of letters and numbers.
 *
 * The class defaults to making a string of length five but can also generate
 * an arbitrary length string. This class is suitable for making low security
 * passwords or keys but may not be entirely secure since it depends on
 * Java's random method.
 *
 * @author  Bill Lynch
 * @version 1.0
 */
public class RandomString {
  public static String randomString() {
    return makeRandom( 5 );
  }

  public static String randomString(int numCharacters) {
    return makeRandom(numCharacters);
  }

  private static String makeRandom(int numChars) {
    String s="";
    int d1, d2;
    char[] letters = initLetters();
    int[]  numbers = initNumbers();

    for( int i=0; i<numChars; i++ ) {
      d1 = ((int)(Math.random()*10)%2);
      if( d1 == 0 ) { // use a letter
        d2 = ((int)(Math.random()*100)%26);
        s += letters[d2];
      }
      else if( d1 == 1 ) { // use a number
        s += (int)(Math.random()*10);
      }
    }
    return s;
  }

  private static char[] initLetters( ) {
    char[] ca = new char[26];
    for( int i=0; i<26; i++ )
      ca[i] = (char)(65 + i);
    return ca;
  }
  private static int[] initNumbers( ) {
    int[] na = new int[10];
    for( int i=0; i<10; i++ )
      na[i] = i;
    return na;
  }
}