我一直在寻找一种简单的Java算法来生成伪随机字母数字字符串。在我的情况下,它将被用作唯一的会话/密钥标识符,“很可能”在超过50万代的时间内是唯一的(我的需求实际上不需要更复杂的东西)。
理想情况下,我可以根据我的独特性需求指定长度。例如,生成的长度为12的字符串可能看起来像“AEYGF7K0DM1X”。
我一直在寻找一种简单的Java算法来生成伪随机字母数字字符串。在我的情况下,它将被用作唯一的会话/密钥标识符,“很可能”在超过50万代的时间内是唯一的(我的需求实际上不需要更复杂的东西)。
理想情况下,我可以根据我的独特性需求指定长度。例如,生成的长度为12的字符串可能看起来像“AEYGF7K0DM1X”。
当前回答
这里是Scala解决方案:
(for (i <- 0 until rnd.nextInt(64)) yield {
('0' + rnd.nextInt(64)).asInstanceOf[Char]
}) mkString("")
其他回答
我使用的是一个非常简单的Java8解决方案。只需根据您的需求进行定制。
...
import java.security.SecureRandom;
...
//Generate a random String of length between 10 to 20.
//Length is also randomly generated here.
SecureRandom random = new SecureRandom();
String sampleSet = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789_";
int stringLength = random.ints(1, 10, 21).mapToObj(x -> x).reduce((a, b) -> a).get();
String randomString = random.ints(stringLength, 0, sampleSet.length() - 1)
.mapToObj(x -> sampleSet.charAt(x))
.collect(Collector
.of(StringBuilder::new, StringBuilder::append,
StringBuilder::append, StringBuilder::toString));
我们可以使用它生成如下的字母数字随机字符串(返回的字符串将强制包含一些非数字字符以及一些数字字符):
public String generateRandomString() {
String sampleSet = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz_";
String sampleSetNumeric = "0123456789";
String randomString = getRandomString(sampleSet, 10, 21);
String randomStringNumeric = getRandomString(sampleSetNumeric, 10, 21);
randomString = randomString + randomStringNumeric;
//Convert String to List<Character>
List<Character> list = randomString.chars()
.mapToObj(x -> (char)x)
.collect(Collectors.toList());
Collections.shuffle(list);
//This is needed to force a non-numeric character as the first String
//Skip this for() if you don't need this logic
for(;;) {
if(Character.isDigit(list.get(0))) Collections.shuffle(list);
else break;
}
//Convert List<Character> to String
randomString = list.stream()
.map(String::valueOf)
.collect(Collectors.joining());
return randomString;
}
//Generate a random number between the lower bound (inclusive) and upper bound (exclusive)
private int getRandomLength(int min, int max) {
SecureRandom random = new SecureRandom();
return random.ints(1, min, max).mapToObj(x -> x).reduce((a, b) -> a).get();
}
//Generate a random String from the given sample string, having a random length between the lower bound (inclusive) and upper bound (exclusive)
private String getRandomString(String sampleSet, int min, int max) {
SecureRandom random = new SecureRandom();
return random.ints(getRandomLength(min, max), 0, sampleSet.length() - 1)
.mapToObj(x -> sampleSet.charAt(x))
.collect(Collector
.of(StringBuilder::new, StringBuilder::append,
StringBuilder::append, StringBuilder::toString));
}
高效而简短。
/**
* Utility class for generating random Strings.
*/
public interface RandomUtil {
int DEF_COUNT = 20;
Random RANDOM = new SecureRandom();
/**
* Generate a password.
*
* @return the generated password
*/
static String generatePassword() {
return generate(true, true);
}
/**
* Generate an activation key.
*
* @return the generated activation key
*/
static String generateActivationKey() {
return generate(false, true);
}
/**
* Generate a reset key.
*
* @return the generated reset key
*/
static String generateResetKey() {
return generate(false, true);
}
static String generate(boolean letters, boolean numbers) {
int
start = ' ',
end = 'z' + 1,
count = DEF_COUNT,
gap = end - start;
StringBuilder builder = new StringBuilder(count);
while (count-- != 0) {
int codePoint = RANDOM.nextInt(gap) + start;
switch (getType(codePoint)) {
case UNASSIGNED:
case PRIVATE_USE:
case SURROGATE:
count++;
continue;
}
int numberOfChars = charCount(codePoint);
if (count == 0 && numberOfChars > 1) {
count++;
continue;
}
if (letters && isLetter(codePoint)
|| numbers && isDigit(codePoint)
|| !letters && !numbers) {
builder.appendCodePoint(codePoint);
if (numberOfChars == 2)
count--;
}
else
count++;
}
return builder.toString();
}
}
在一行中:
Long.toHexString(Double.doubleToLongBits(Math.random()));
来源:Java-生成随机字符串
import java.util.Date;
import java.util.Random;
public class RandomGenerator {
private static Random random = new Random((new Date()).getTime());
public static String generateRandomString(int length) {
char[] values = {'a','b','c','d','e','f','g','h','i','j',
'k','l','m','n','o','p','q','r','s','t',
'u','v','w','x','y','z','0','1','2','3',
'4','5','6','7','8','9'};
String out = "";
for (int i=0;i<length;i++) {
int idx=random.nextInt(values.length);
out += values[idx];
}
return out;
}
}
Java 8中的另一种选择是:
static final Random random = new Random(); // Or SecureRandom
static final int startChar = (int) '!';
static final int endChar = (int) '~';
static String randomString(final int maxLength) {
final int length = random.nextInt(maxLength + 1);
return random.ints(length, startChar, endChar + 1)
.collect(StringBuilder::new, StringBuilder::appendCodePoint, StringBuilder::append)
.toString();
}