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
* <jsp:getProperty name=<i>"id"</i> property="randomstr"/>
*
* @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");
}
}