java 随机产生字符串

 
package mysite;

import java.util.*;
import java.security.SecureRandom;
import java.security.NoSuchAlgorithmException;
import java.security.NoSuchProviderException;

public class RandomStrg {

    private Integer length = new Integer(8);
    public void setLength(int count){ length =new Integer(count);}

    private String randomstr;
    private boolean allchars = false;
   
    private HashMap hmap;
    private ArrayList lower = null;
    private ArrayList upper = null;
    private char[] single = null;
    private int singlecount = 0;
    private boolean singles = false;
    private String algorithm = null;
    private String provider = null;
    private boolean secure = false;
    private Random random = null;
    private SecureRandom secrandom = null;

    private final float getFloat() {
 if (random == null)
     return secrandom.nextFloat();
 else
     return random.nextFloat();
    }

    /**
     * generate the Random object that will be used for this random number
     * generator
     *
     */
    public final void generateRandomObject() throws Exception {

 // check to see if the object is a SecureRandom object
 if (secure) {
     try {
  // get an instance of a SecureRandom object
  if (provider != null)
      // search for algorithm in package provider
      random = SecureRandom.getInstance(algorithm, provider);
  else
      random = SecureRandom.getInstance(algorithm);
     } catch (NoSuchAlgorithmException ne) {
  throw new Exception(ne.getMessage());
     } catch (NoSuchProviderException pe) {
  throw new Exception(pe.getMessage());
     }
 } else
     random = new Random();
    }

    /**
     * generate the random string
     *
     */
    private final void generaterandom() {

 if (allchars)
     for (int i = 0; i < length.intValue(); i++)
  randomstr = randomstr + new Character((char)((int) 34 +
         ((int)(getFloat() * 93)))).toString();
 else if (singles) {
     // check if there are single chars to be included

     if (upper.size() == 3) {
  // check for the number of ranges max 3 uppercase lowercase digits

  // build the random string
  for (int i = 0; i < length.intValue(); i++) {
      // you have four groups to choose a random number from, to make
      // the choice a little more random select a number out of 100

      // get a random number even or odd
      if (((int) (getFloat() * 100)) % 2 == 0) {

   // the number was even get another number even or odd
   if (((int) (getFloat() * 100)) % 2 == 0)
       // choose a random char from the single char group
       randomstr = randomstr + randomSingle().toString();
   else
       // get a random char from the first range
       randomstr = randomstr + randomChar((Character)lower.get(2),
      (Character)upper.get(2)).toString();
      } else {
   // the number was odd

   if (((int) (getFloat() * 100)) % 2 == 0)
       // choose a random char from the second range
       randomstr = randomstr + randomChar((Character)lower.get(1),
            (Character)upper.get(1)).toString();
   else
       // choose a random char from the third range
       randomstr = randomstr + randomChar((Character)lower.get(0), 
            (Character)upper.get(0)).toString();
      }
  }
     } else if (upper.size() == 2) {
  // single chars are to be included choose a random char from
  // two different ranges

  // build the random char from single chars and two ranges
  for (int i = 0; i < length.intValue(); i++) {
      // select the single chars or a range to get each random char
      // from

      if (((int)(getFloat() * 100)) % 2 == 0) {

   // get random char from the single chars
   randomstr = randomstr + randomSingle().toString();
      } else if (((int) (getFloat() * 100)) % 2 == 0) {

   // get the random char from the first range
   randomstr = randomstr + randomChar((Character)lower.get(1),
            (Character)upper.get(1)).toString();
      } else {

   // get the random char from the second range
   randomstr = randomstr + randomChar((Character)lower.get(0),
            (Character)upper.get(0)).toString();
      }
  }
     } else if (upper.size() == 1) {

  // build the random string from single chars and one range
  for (int i = 0; i < length.intValue(); i++) {
      if (((int) getFloat() * 100) % 2 == 0)
   // get a random single char
   randomstr = randomstr + randomSingle().toString();
      else
   // get a random char from the range
   randomstr = randomstr + randomChar((Character)lower.get(0),
            (Character)upper.get(0)).toString();
  }
     } else {
  // build the rand string from single chars
  for (int i = 0; i < length.intValue(); i++)
      randomstr = randomstr + randomSingle().toString();
     }
 } else {

     // no single chars are to be included in the random string
     if (upper.size() == 3) {

  // build random strng from three ranges
  for (int i = 0; i < length.intValue(); i++) {

      if (((int) (getFloat() * 100)) % 2 == 0) {

   // get random char from first range
   randomstr = randomstr + randomChar((Character)lower.get(2),
            (Character)upper.get(2)).toString();
      } else if (((int) (getFloat() * 100)) % 2 == 0) {

   // get random char form second range
   randomstr = randomstr + randomChar((Character)lower.get(1),
            (Character)upper.get(1)).toString();
      } else {

   // get random char from third range
   randomstr = randomstr + randomChar((Character)lower.get(0),
            (Character)upper.get(0)).toString();
      }
  }
     } else if (upper.size() == 2) {

  // build random string from two ranges
  for (int i = 0; i < length.intValue(); i++) {
      if (((int) (getFloat() * 100)) % 2 == 0)
   // get random char from first range
   randomstr = randomstr + randomChar((Character)lower.get(1),
            (Character)upper.get(1)).toString();
      else
   // get random char from second range
   randomstr = randomstr + randomChar((Character)lower.get(0),
          (Character)upper.get(0)).toString();
  }
     } else

  // build random string
  for (int i = 0; i < length.intValue(); i++)
      // get random char from only range
      randomstr = randomstr + randomChar((Character)lower.get(0),
            (Character)upper.get(0)).toString();
 }
    }

    /**
     * generate a random char from the single char list
     *
     * @returns - a randomly selscted character from the single char list
     *
     */
    private final Character randomSingle() {

 return (new Character(single[(int)((getFloat() * singlecount) - 1)]));
    }

    /**
     * generate a random character
     *
     * @param lower  lower bound from which to get a random char
     * @param upper  upper bound from which to get a random char
     *
     * @returns - a randomly generated character
     *
     */
    private final Character randomChar(Character lower, Character upper) {
 int tempval;
 char low = lower.charValue();
 char up = upper.charValue();

 // get a random number in the range lowlow - lowup
 tempval = (int)((int)low + (getFloat() * ((int)(up - low))));

 // return the random char
 return (new Character((char) tempval));
    }

    /**
     * get the randomly created string for use with the
     * &lt;jsp:getProperty name=<i>"id"</i> property="randomstr"/&gt;
     *
     * @return - randomly created string
     *
     */
    public final String getRandom() {

 randomstr = new String();

 generaterandom(); // generate the first random string

 if (hmap != null) {

     while (hmap.containsKey(randomstr)) {
  // random string has already been created generate a different one
  generaterandom();
     }

     hmap.put(randomstr, null);  // add the new random string
 }

 return randomstr;
    }

    /**
     * set the ranges from which to choose the characters for the random string
     *
     * @param low  set of lower ranges
     * @param up  set of upper ranges
     *
     */
    public final void setRanges(ArrayList low, ArrayList up) {
 lower = low;
 upper = up;
    }

    /**
     * set the hashmap that is used to check the uniqueness of random strings
     *
     * @param map  hashmap whose keys are used to insure uniqueness of random strgs
     *
     */
    public final void setHmap(HashMap map) {
 hmap = map;
    }

    /**
     * set the length of the random string
     *
     * @param value  length of the random string
     *
     */
    public final void setLength(String value) {
     length = new Integer(value);
    
    }

    /**
     * set the algorithm name
     *
     * @param value  name of the algorithm to use for a SecureRandom object
     *
     */
    public final void setAlgorithm(String value) {
 algorithm = value;
 secure = true;  // a SecureRandom object is to be used
    }

    /**
     * set the provider name
     *
     * @param value  name of the package to check for the algorithm
     *
     */
    public final void setProvider(String value) {
 provider = value;
    }

    /**
     * set the allchars flag
     *
     * @param value  boolean value of the allchars flag
     *
     */
    public final void setAllchars(boolean value) {
 allchars = value;
    }

    /**
     * set the array of single chars to choose from for this random string and the
     * number of chars in the array
     *
     * @param chars  the array of single chars
     * @param value  the number of single chars
     *
     */
    public final void setSingle(char[] chars, int value) {
 single = chars;  // set the array of chars
 singlecount = value;  // set the number of chars in array single
 singles = true;  // set flag that single chars are in use
    }
   
    public final void setCharset(String value)
    {
    // values tells the method whether or not to check for single chars
    boolean more = true;

    // create the arraylists to hold the upper and lower bounds for the char
   // ranges
   lower = new ArrayList(3);
   upper = new ArrayList(3);

   // user has chosen to use all possible characters in the random string
   if (value.compareTo("all") == 0) {
     allchars = true;  // set allchars flag
     // all chars are to be used so there are no single chars to sort
     // through
     more = false;
   }else if ((value.charAt(1) == '-') && (value.charAt(0) != '//')) {
     // run through the ranges at most 3
     while (more && (value.charAt(1) == '-')){

      // check to make sure that the dash is not the single char
         if (value.charAt(0) == '//')
             break;
        else {
          // add upper and lower ranges to there list
          lower.add(new Character(value.charAt(0)));
          upper.add(new Character(value.charAt(2)));
      }

      // check to see if there is more to the charset
      if (value.length() <= 3)
            more = false;
      else
            // create a new string so that the next range if there is one
         // starts it
         value = value.substring(3);
      }
 }

 // if more = false there are no single chars in the charset
 if (more) {

     single = new char[30];  // create single

     // create a set of tokens from the string of single chars
     StringTokenizer tokens = new StringTokenizer(value);

     while (tokens.hasMoreTokens()) {
  // get the next token from the string
  String token = tokens.nextToken();

  if (token.length() > 1)
      // char is a - add it to the list
      single[singlecount++] = '-';

  // add the current char to the list
  single[singlecount++] = token.charAt(0);
     }
 }
    if ((lower == null) && (single == null))
     setCharset("a-zA-Z0-9"); 
  }
}