我一直在寻找一个简单的Java算法来生成伪随机的字母数字字符串。在我的情况下,它将被用作唯一的会话/键标识符,可能在500K+次生成中是唯一的(我的需求并不需要更复杂的东西)。
理想情况下,我希望能够根据我的唯一性需求指定长度。例如,长度为12的生成字符串可能看起来像"AEYGF7K0DM1X"
。
我一直在寻找一个简单的Java算法来生成伪随机的字母数字字符串。在我的情况下,它将被用作唯一的会话/键标识符,可能在500K+次生成中是唯一的(我的需求并不需要更复杂的东西)。
理想情况下,我希望能够根据我的唯一性需求指定长度。例如,长度为12的生成字符串可能看起来像"AEYGF7K0DM1X"
。
给定一些字符(AllCharacters
),您可以随机选择字符串中的一个字符。然后使用for循环重复获取随机字符。
public class MyProgram {
static String getRandomString(int size) {
String AllCharacters = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";
StringBuilder sb = new StringBuilder(size);
int length = AllCharacters.length();
for (int i = 0; i < size; i++) {
sb.append(AllCharacters.charAt((int)(length * Math.random())));
}
return sb.toString();
}
public static void main(String[] args) {
System.out.println(MyProgram.getRandomString(30));
}
}
public static String RandomAlphanum(int length)
{
String charstring = "abcdefghijklmnopqrstuvwxyz0123456789";
String randalphanum = "";
double randroll;
String randchar;
for (double i = 0; i < length; i++)
{
randroll = Math.random();
randchar = "";
for (int j = 1; j <= 35; j++)
{
if (randroll <= (1.0 / 36.0 * j))
{
randchar = Character.toString(charstring.charAt(j - 1));
break;
}
}
randalphanum += randchar;
}
return randalphanum;
}
我使用了一个非常原始的算法,使用了 Math.random()。为了增加随机性,您可以直接实现 util.Date 类。尽管如此,它仍然有效。
同时,您可以通过ASCII表中的数据生成任何小写或大写字母甚至特殊字符。例如,从A(DEC 65)到Z(DEC 90)生成大写字母:
String generateRandomStr(int min, int max, int size) {
String result = "";
for (int i = 0; i < size; i++) {
result += String.valueOf((char)(new Random().nextInt((max - min) + 1) + min));
}
return result;
}
生成 generateRandomStr(65, 90, 100));
的输出:
TVLPFQJCYFXQDCQSLKUKKILKKHAUFYEXLUQFHDWNMRBIRRRWNXNNZQTINZPCTKLHGHVYWRKEOYNSOFPZBGEECFMCOKWHLHCEWLDZ
高效且简洁。
/**
* 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();
}
}
另一种解决方案...
public static String generatePassword(int passwordLength) {
int asciiFirst = 33;
int asciiLast = 126;
Integer[] exceptions = { 34, 39, 96 };
List<Integer> exceptionsList = Arrays.asList(exceptions);
SecureRandom random = new SecureRandom();
StringBuilder builder = new StringBuilder();
for (int i=0; i<passwordLength; i++) {
int charIndex;
do {
charIndex = random.nextInt(asciiLast - asciiFirst + 1) + asciiFirst;
}
while (exceptionsList.contains(charIndex));
builder.append((char) charIndex);
}
return builder.toString();
}
我正在使用一个非常简单的Java 8解决方案。根据您的需求进行自定义即可。
...
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));
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));
}
Long.toHexString(Double.doubleToLongBits(Math.random()));
生成一个16进制的随机字符串。UUID.randomUUID().toString();
生成一个随机唯一标识符。RandomStringUtils.randomAlphanumeric(12);
生成一个包含12个字符的随机字母数字组合。 - Manindar