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
最佳随机字符串生成器方法
public class RandomStringGenerator{
private static int randomStringLength = 25 ;
private static boolean allowSpecialCharacters = true ;
private static String specialCharacters = "!@$%*-_+:";
private static boolean allowDuplicates = false ;
private static boolean isAlphanum = false;
private static boolean isNumeric = false;
private static boolean isAlpha = false;
private static final String alphabet = "abcdefghijklmnopqrstuvwxyz";
private static boolean mixCase = false;
private static final String capAlpha = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
private static final String num = "0123456789";
public static String getRandomString() {
String returnVal = "";
int specialCharactersCount = 0;
int maxspecialCharacters = randomStringLength/4;
try {
StringBuffer values = buildList();
for (int inx = 0; inx < randomStringLength; inx++) {
int selChar = (int) (Math.random() * (values.length() - 1));
if (allowSpecialCharacters)
{
if (specialCharacters.indexOf("" + values.charAt(selChar)) > -1)
{
specialCharactersCount ++;
if (specialCharactersCount > maxspecialCharacters)
{
while (specialCharacters.indexOf("" + values.charAt(selChar)) != -1)
{
selChar = (int) (Math.random() * (values.length() - 1));
}
}
}
}
returnVal += values.charAt(selChar);
if (!allowDuplicates) {
values.deleteCharAt(selChar);
}
}
} catch (Exception e) {
returnVal = "Error While Processing Values";
}
return returnVal;
}
private static StringBuffer buildList() {
StringBuffer list = new StringBuffer(0);
if (isNumeric || isAlphanum) {
list.append(num);
}
if (isAlpha || isAlphanum) {
list.append(alphabet);
if (mixCase) {
list.append(capAlpha);
}
}
if (allowSpecialCharacters)
{
list.append(specialCharacters);
}
int currLen = list.length();
String returnVal = "";
for (int inx = 0; inx < currLen; inx++) {
int selChar = (int) (Math.random() * (list.length() - 1));
returnVal += list.charAt(selChar);
list.deleteCharAt(selChar);
}
list = new StringBuffer(returnVal);
return list;
}
}
其他回答
在一行中：
Long.toHexString(Double.doubleToLongBits(Math.random()));
来源：Java-生成随机字符串
最佳随机字符串生成器方法
public class RandomStringGenerator{
private static int randomStringLength = 25 ;
private static boolean allowSpecialCharacters = true ;
private static String specialCharacters = "!@$%*-_+:";
private static boolean allowDuplicates = false ;
private static boolean isAlphanum = false;
private static boolean isNumeric = false;
private static boolean isAlpha = false;
private static final String alphabet = "abcdefghijklmnopqrstuvwxyz";
private static boolean mixCase = false;
private static final String capAlpha = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
private static final String num = "0123456789";
public static String getRandomString() {
String returnVal = "";
int specialCharactersCount = 0;
int maxspecialCharacters = randomStringLength/4;
try {
StringBuffer values = buildList();
for (int inx = 0; inx < randomStringLength; inx++) {
int selChar = (int) (Math.random() * (values.length() - 1));
if (allowSpecialCharacters)
{
if (specialCharacters.indexOf("" + values.charAt(selChar)) > -1)
{
specialCharactersCount ++;
if (specialCharactersCount > maxspecialCharacters)
{
while (specialCharacters.indexOf("" + values.charAt(selChar)) != -1)
{
selChar = (int) (Math.random() * (values.length() - 1));
}
}
}
}
returnVal += values.charAt(selChar);
if (!allowDuplicates) {
values.deleteCharAt(selChar);
}
}
} catch (Exception e) {
returnVal = "Error While Processing Values";
}
return returnVal;
}
private static StringBuffer buildList() {
StringBuffer list = new StringBuffer(0);
if (isNumeric || isAlphanum) {
list.append(num);
}
if (isAlpha || isAlphanum) {
list.append(alphabet);
if (mixCase) {
list.append(capAlpha);
}
}
if (allowSpecialCharacters)
{
list.append(specialCharacters);
}
int currLen = list.length();
String returnVal = "";
for (int inx = 0; inx < currLen; inx++) {
int selChar = (int) (Math.random() * (list.length() - 1));
returnVal += list.charAt(selChar);
list.deleteCharAt(selChar);
}
list = new StringBuffer(returnVal);
return list;
}
}
另一个解决方案。。。
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();
}
使用美元应简单如下：
// "0123456789" + "ABCDE...Z"
String validCharacters = $('0', '9').join() + $('A', 'Z').join();
String randomString(int length) {
return $(validCharacters).shuffle().slice(length).toString();
}
@Test
public void buildFiveRandomStrings() {
for (int i : $(5)) {
System.out.println(randomString(12));
}
}
它输出的内容如下：
DKL1SBH9UJWC
JH7P0IT21EA5
5DTI72EO6SFU
HQUMJTEBNF7Y
1HCR6SKYWGT7
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));
}
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