package cn.trinea.android.common.util;
import java.util.Random;
/**
* Random Utils
* <ul>
* Shuffling algorithm
* <li>{@link #shuffle(Object[])} Shuffling algorithm, Randomly permutes the specified array using a default source of
* randomness</li>
* <li>{@link #shuffle(Object[], int)} Shuffling algorithm, Randomly permutes the specified array</li>
* <li>{@link #shuffle(int[])} Shuffling algorithm, Randomly permutes the specified int array using a default source of
* randomness</li>
* <li>{@link #shuffle(int[], int)} Shuffling algorithm, Randomly permutes the specified int array</li>
* </ul>
* <ul>
* get random int
* <li>{@link #getRandom(int)} get random int between 0 and max</li>
* <li>{@link #getRandom(int, int)} get random int between min and max</li>
* </ul>
* <ul>
* get random numbers or letters
* <li>{@link #getRandomCapitalLetters(int)} get a fixed-length random string, its a mixture of uppercase letters</li>
* <li>{@link #getRandomLetters(int)} get a fixed-length random string, its a mixture of uppercase and lowercase letters
* </li>
* <li>{@link #getRandomLowerCaseLetters(int)} get a fixed-length random string, its a mixture of lowercase letters</li>
* <li>{@link #getRandomNumbers(int)} get a fixed-length random string, its a mixture of numbers</li>
* <li>{@link #getRandomNumbersAndLetters(int)} get a fixed-length random string, its a mixture of uppercase, lowercase
* letters and numbers</li>
* <li>{@link #getRandom(String, int)} get a fixed-length random string, its a mixture of chars in source</li>
* <li>{@link #getRandom(char[], int)} get a fixed-length random string, its a mixture of chars in sourceChar</li>
* </ul>
*
* @author <a href="http://www.trinea.cn" target="_blank">Trinea</a> 2012-5-12
*/
public class RandomUtils {
public static final String NUMBERS_AND_LETTERS = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
public static final String NUMBERS = "0123456789";
public static final String LETTERS = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
public static final String CAPITAL_LETTERS = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
public static final String LOWER_CASE_LETTERS = "abcdefghijklmnopqrstuvwxyz";
private RandomUtils() {
throw new AssertionError();
}
/**
* get a fixed-length random string, its a mixture of uppercase, lowercase letters and numbers
*
* @param length
* @return
* @see cn.trinea.android.common.util.RandomUtils#getRandom(String source, int length)
*/
public static String getRandomNumbersAndLetters(int length) {
return getRandom(NUMBERS_AND_LETTERS, length);
}
/**
* get a fixed-length random string, its a mixture of numbers
*
* @param length
* @return
* @see cn.trinea.android.common.util.RandomUtils#getRandom(String source, int length)
*/
public static String getRandomNumbers(int length) {
return getRandom(NUMBERS, length);
}
/**
* get a fixed-length random string, its a mixture of uppercase and lowercase letters
*
* @param length
* @return
* @see cn.trinea.android.common.util.RandomUtils#getRandom(String source, int length)
*/
public static String getRandomLetters(int length) {
return getRandom(LETTERS, length);
}
/**
* get a fixed-length random string, its a mixture of uppercase letters
*
* @param length
* @return
* @see cn.trinea.android.common.util.RandomUtils#getRandom(String source, int length)
*/
public static String getRandomCapitalLetters(int length) {
return getRandom(CAPITAL_LETTERS, length);
}
/**
* get a fixed-length random string, its a mixture of lowercase letters
*
* @param length
* @return
* @see cn.trinea.android.common.util.RandomUtils#getRandom(String source, int length)
*/
public static String getRandomLowerCaseLetters(int length) {
return getRandom(LOWER_CASE_LETTERS, length);
}
/**
* get a fixed-length random string, its a mixture of chars in source
*
* @param source
* @param length
* @return <ul>
* <li>if source is null or empty, return null</li>
* <li>else see {@link cn.trinea.android.common.util.RandomUtils#getRandom(char[] sourceChar, int length)}</li>
* </ul>
*/
public static String getRandom(String source, int length) {
return StringUtils.isEmpty(source) ? null : getRandom(source.toCharArray(), length);
}
/**
* get a fixed-length random string, its a mixture of chars in sourceChar
*
* @param sourceChar
* @param length
* @return <ul>
* <li>if sourceChar is null or empty, return null</li>
* <li>if length less than 0, return null</li>
* </ul>
*/
public static String getRandom(char[] sourceChar, int length) {
if (sourceChar == null || sourceChar.length == 0 || length < 0) {
return null;
}
StringBuilder str = new StringBuilder(length);
Random random = new Random();
for (int i = 0; i < length; i++) {
str.append(sourceChar[random.nextInt(sourceChar.length)]);
}
return str.toString();
}
/**
* get random int between 0 and max
*
* @param max
* @return <ul>
* <li>if max <= 0, return 0</li>
* <li>else return random int between 0 and max</li>
* </ul>
*/
public static int getRandom(int max) {
return getRandom(0, max);
}
/**
* get random int between min and max
*
* @param min
* @param max
* @return <ul>
* <li>if min > max, return 0</li>
* <li>if min == max, return min</li>
* <li>else return random int between min and max</li>
* </ul>
*/
public static int getRandom(int min, int max) {
if (min > max) {
return 0;
}
if (min == max) {
return min;
}
return min + new Random().nextInt(max - min);
}
/**
* Shuffling algorithm, Randomly permutes the specified array using a default source of randomness
*
* @param objArray
* @return
*/
public static boolean shuffle(Object[] objArray) {
if (objArray == null) {
return false;
}
return shuffle(objArray, getRandom(objArray.length));
}
/**
* Shuffling algorithm, Randomly permutes the specified array
*
* @param objArray
* @param shuffleCount
* @return
*/
public static boolean shuffle(Object[] objArray, int shuffleCount) {
int length;
if (objArray == null || shuffleCount < 0 || (length = objArray.length) < shuffleCount) {
return false;
}
for (int i = 1; i <= shuffleCount; i++) {
int random = getRandom(length - i);
Object temp = objArray[length - i];
objArray[length - i] = objArray[random];
objArray[random] = temp;
}
return true;
}
/**
* Shuffling algorithm, Randomly permutes the specified int array using a default source of randomness
*
* @param intArray
* @return
*/
public static int[] shuffle(int[] intArray) {
if (intArray == null) {
return null;
}
return shuffle(intArray, getRandom(intArray.length));
}
/**
* Shuffling algorithm, Randomly permutes the specified int array
*
* @param intArray
* @param shuffleCount
* @return
*/
public static int[] shuffle(int[] intArray, int shuffleCount) {
int length;
if (intArray == null || shuffleCount < 0 || (length = intArray.length) < shuffleCount) {
return null;
}
int[] out = new int[shuffleCount];
for (int i = 1; i <= shuffleCount; i++) {
int random = getRandom(length - i);
out[i - 1] = intArray[random];
int temp = intArray[length - i];
intArray[length - i] = intArray[random];
intArray[random] = temp;
}
return out;
}
}