Operations for random Strings
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* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
import java.util.Random;
/**
* <p>Operations for random <code>String</code>s.</p>
* <p>Currently <em>private high surrogate</em> characters are ignored.
* These are unicode characters that fall between the values 56192 (db80)
* and 56319 (dbff) as we don't know how to handle them.
* High and low surrogates are correctly dealt with - that is if a
* high surrogate is randomly chosen, 55296 (d800) to 56191 (db7f)
* then it is followed by a low surrogate. If a low surrogate is chosen,
* 56320 (dc00) to 57343 (dfff) then it is placed after a randomly
* chosen high surrogate. </p>
*
* @author <a href="mailto:steven@caswell.name">Steven Caswell</a>
* @author Stephen Colebourne
* @author Gary Gregory
* @author Phil Steitz
* @since 1.0
* @version $Id: RandomStringUtils.java 471626 2006-11-06 04:02:09Z bayard $
*/
public class RandomStringUtils {
/**
* <p>Random object used by random method. This has to be not local
* to the random method so as to not return the same value in the
* same millisecond.</p>
*/
private static final Random RANDOM = new Random();
/**
* <p><code>RandomStringUtils</code> instances should NOT be constructed in
* standard programming. Instead, the class should be used as
* <code>RandomStringUtils.random(5);</code>.</p>
*
* <p>This constructor is public to permit tools that require a JavaBean instance
* to operate.</p>
*/
public RandomStringUtils() {
super();
}
// Random
//-----------------------------------------------------------------------
/**
* <p>Creates a random string whose length is the number of characters
* specified.</p>
*
* <p>Characters will be chosen from the set of all characters.</p>
*
* @param count the length of random string to create
* @return the random string
*/
public static String random(int count) {
return random(count, false, false);
}
/**
* <p>Creates a random string whose length is the number of characters
* specified.</p>
*
* <p>Characters will be chosen from the set of characters whose
* ASCII value is between <code>32</code> and <code>126</code> (inclusive).</p>
*
* @param count the length of random string to create
* @return the random string
*/
public static String randomAscii(int count) {
return random(count, 32, 127, false, false);
}
/**
* <p>Creates a random string whose length is the number of characters
* specified.</p>
*
* <p>Characters will be chosen from the set of alphabetic
* characters.</p>
*
* @param count the length of random string to create
* @return the random string
*/
public static String randomAlphabetic(int count) {
return random(count, true, false);
}
/**
* <p>Creates a random string whose length is the number of characters
* specified.</p>
*
* <p>Characters will be chosen from the set of alpha-numeric
* characters.</p>
*
* @param count the length of random string to create
* @return the random string
*/
public static String randomAlphanumeric(int count) {
return random(count, true, true);
}
/**
* <p>Creates a random string whose length is the number of characters
* specified.</p>
*
* <p>Characters will be chosen from the set of numeric
* characters.</p>
*
* @param count the length of random string to create
* @return the random string
*/
public static String randomNumeric(int count) {
return random(count, false, true);
}
/**
* <p>Creates a random string whose length is the number of characters
* specified.</p>
*
* <p>Characters will be chosen from the set of alpha-numeric
* characters as indicated by the arguments.</p>
*
* @param count the length of random string to create
* @param letters if <code>true</code>, generated string will include
* alphabetic characters
* @param numbers if <code>true</code>, generated string will include
* numeric characters
* @return the random string
*/
public static String random(int count, boolean letters, boolean numbers) {
return random(count, 0, 0, letters, numbers);
}
/**
* <p>Creates a random string whose length is the number of characters
* specified.</p>
*
* <p>Characters will be chosen from the set of alpha-numeric
* characters as indicated by the arguments.</p>
*
* @param count the length of random string to create
* @param start the position in set of chars to start at
* @param end the position in set of chars to end before
* @param letters if <code>true</code>, generated string will include
* alphabetic characters
* @param numbers if <code>true</code>, generated string will include
* numeric characters
* @return the random string
*/
public static String random(int count, int start, int end, boolean letters, boolean numbers) {
return random(count, start, end, letters, numbers, null, RANDOM);
}
/**
* <p>Creates a random string based on a variety of options, using
* default source of randomness.</p>
*
* <p>This method has exactly the same semantics as
* {@link #random(int,int,int,boolean,boolean,char[],Random)}, but
* instead of using an externally supplied source of randomness, it uses
* the internal static {@link Random} instance.</p>
*
* @param count the length of random string to create
* @param start the position in set of chars to start at
* @param end the position in set of chars to end before
* @param letters only allow letters?
* @param numbers only allow numbers?
* @param chars the set of chars to choose randoms from.
* If <code>null</code>, then it will use the set of all chars.
* @return the random string
* @throws ArrayIndexOutOfBoundsException if there are not
* <code>(end - start) + 1</code> characters in the set array.
*/
public static String random(int count, int start, int end, boolean letters, boolean numbers, char[] chars) {
return random(count, start, end, letters, numbers, chars, RANDOM);
}
/**
* <p>Creates a random string based on a variety of options, using
* supplied source of randomness.</p>
*
* <p>If start and end are both <code>0</code>, start and end are set
* to <code>' '</code> and <code>'z'</code>, the ASCII printable
* characters, will be used, unless letters and numbers are both
* <code>false</code>, in which case, start and end are set to
* <code>0</code> and <code>Integer.MAX_VALUE</code>.
*
* <p>If set is not <code>null</code>, characters between start and
* end are chosen.</p>
*
* <p>This method accepts a user-supplied {@link Random}
* instance to use as a source of randomness. By seeding a single
* {@link Random} instance with a fixed seed and using it for each call,
* the same random sequence of strings can be generated repeatedly
* and predictably.</p>
*
* @param count the length of random string to create
* @param start the position in set of chars to start at
* @param end the position in set of chars to end before
* @param letters only allow letters?
* @param numbers only allow numbers?
* @param chars the set of chars to choose randoms from.
* If <code>null</code>, then it will use the set of all chars.
* @param random a source of randomness.
* @return the random string
* @throws ArrayIndexOutOfBoundsException if there are not
* <code>(end - start) + 1</code> characters in the set array.
* @throws IllegalArgumentException if <code>count</code> < 0.
* @since 2.0
*/
public static String random(int count, int start, int end, boolean letters, boolean numbers,
char[] chars, Random random) {
if (count == 0) {
return "";
} else if (count < 0) {
throw new IllegalArgumentException("Requested random string length " + count + " is less than 0.");
}
if ((start == 0) && (end == 0)) {
end = 'z' + 1;
start = ' ';
if (!letters && !numbers) {
start = 0;
end = Integer.MAX_VALUE;
}
}
char[] buffer = new char[count];
int gap = end - start;
while (count-- != 0) {
char ch;
if (chars == null) {
ch = (char) (random.nextInt(gap) + start);
} else {
ch = chars[random.nextInt(gap) + start];
}
if ((letters && Character.isLetter(ch))
|| (numbers && Character.isDigit(ch))
|| (!letters && !numbers))
{
if(ch >= 56320 && ch <= 57343) {
if(count == 0) {
count++;
} else {
// low surrogate, insert high surrogate after putting it in
buffer[count] = ch;
count--;
buffer[count] = (char) (55296 + random.nextInt(128));
}
} else if(ch >= 55296 && ch <= 56191) {
if(count == 0) {
count++;
} else {
// high surrogate, insert low surrogate before putting it in
buffer[count] = (char) (56320 + random.nextInt(128));
count--;
buffer[count] = ch;
}
} else if(ch >= 56192 && ch <= 56319) {
// private high surrogate, no effing clue, so skip it
count++;
} else {
buffer[count] = ch;
}
} else {
count++;
}
}
return new String(buffer);
}
/**
* <p>Creates a random string whose length is the number of characters
* specified.</p>
*
* <p>Characters will be chosen from the set of characters
* specified.</p>
*
* @param count the length of random string to create
* @param chars the String containing the set of characters to use,
* may be null
* @return the random string
* @throws IllegalArgumentException if <code>count</code> < 0.
*/
public static String random(int count, String chars) {
if (chars == null) {
return random(count, 0, 0, false, false, null, RANDOM);
}
return random(count, chars.toCharArray());
}
/**
* <p>Creates a random string whose length is the number of characters
* specified.</p>
*
* <p>Characters will be chosen from the set of characters specified.</p>
*
* @param count the length of random string to create
* @param chars the character array containing the set of characters to use,
* may be null
* @return the random string
* @throws IllegalArgumentException if <code>count</code> < 0.
*/
public static String random(int count, char[] chars) {
if (chars == null) {
return random(count, 0, 0, false, false, null, RANDOM);
}
return random(count, 0, chars.length, false, false, chars, RANDOM);
}
}
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