这个问题在这里已有答案：
我正在寻找在Java中创建一个唯一ID作为String的最佳方法。
任何指导表示赞赏，谢谢。
我应该提到我正在使用Java 5。
创建一个UUID。
String uniqueID = UUID.randomUUID().toString();
带有计数信息的唯一ID
import java.util.concurrent.atomic.AtomicLong;
public class RandomIdUtils {
private static AtomicLong atomicCounter = new AtomicLong();
public static String createId() {
String currentCounter = String.valueOf(atomicCounter.getAndIncrement());
String uniqueId = UUID.randomUUID().toString();
return uniqueId + "-" + currentCounter;
}
}
String name,password;
public int idGen() {
int id = this.name.hashCode() + this.password.hashCode();
int length = String.valueOf(id).length();
int Max_Length = 5;
if(String.valueOf(id).length()>Max_Length)
{
id = (int) (id /Math.pow(10.0,length - Max_Length ));
}
return id;
}
enter code here
class Test {
public static void main(String arg[]) {
String s = "";
double d;
for (int i = 1; i <= 16; i++) {
d = Math.random() * 10;
s = s + ((int)d);
if (i % 4 == 0 && i != 16) {
s = s + "-";
}
}
System.out.println(s);
}
}
7954-7605-1827-4795
1991-4912-4912-3008
如果您需要简短的，人类可读的ID，并且每个JVM运行只需要它们是唯一的：
private static long idCounter = 0;
public static synchronized String createID()
{
return String.valueOf(idCounter++);
}
编辑：评论中建议的替代方案 - 这依赖于线程安全的底层“魔力”，但更具可扩展性，同样安全：
private static AtomicLong idCounter = new AtomicLong();
public static String createID()
{
return String.valueOf(idCounter.getAndIncrement());
}
java.util.UUID：toString（）方法
这是我的两分钱：我之前已经实现了一个IdFactory类，它以[主机名] - [应用程序开始时间] - [当前时间] - [鉴别器]的格式创建ID。这在很大程度上保证了ID在JVM实例中是唯一的，同时保持ID可读（尽管很长）。这是代码，以防任何用途：
public class IdFactoryImpl implements IdFactory {
private final String hostName;
private final long creationTimeMillis;
private long lastTimeMillis;
private long discriminator;
public IdFactoryImpl() throws UnknownHostException {
this.hostName = InetAddress.getLocalHost().getHostAddress();
this.creationTimeMillis = System.currentTimeMillis();
this.lastTimeMillis = creationTimeMillis;
}
public synchronized Serializable createId() {
String id;
long now = System.currentTimeMillis();
if (now == lastTimeMillis) {
++discriminator;
} else {
discriminator = 0;
}
// creationTimeMillis used to prevent multiple instances of the JVM
// running on the same host returning clashing IDs.
// The only way a clash could occur is if the applications started at
// exactly the same time.
id = String.format("%s-%d-%d-%d", hostName, creationTimeMillis, now, discriminator);
lastTimeMillis = now;
return id;
}
public static void main(String[] args) throws UnknownHostException {
IdFactory fact = new IdFactoryImpl();
for (int i=0; i<1000; ++i) {
System.err.println(fact.createId());
}
}
}
这为UUID生成添加了更多随机性，但确保每个生成的id具有相同的长度
import org.apache.commons.codec.digest.DigestUtils;
import java.util.UUID;
public String createSalt() {
String ts = String.valueOf(System.currentTimeMillis());
String rand = UUID.randomUUID().toString();
return DigestUtils.sha1Hex(ts + rand);
}
Java - 生成唯一ID
UUID是在Java中生成唯一ID的最快速，最简单的方法。
import java.util.UUID;
public class UniqueIDTest {
public static void main(String[] args) {
UUID uniqueKey = UUID.randomUUID();
System.out.println (uniqueKey);
}
}
恕我直言aperkins提供了一个优雅的解决方案原因是本机和使用较少的代码。但是如果你需要一个较短的ID，你可以使用这种方法来减少生成的String长度：
// usage: GenerateShortUUID.next();
import java.util.UUID;
public class GenerateShortUUID() {
private GenerateShortUUID() { } // singleton
public static String next() {
UUID u = UUID.randomUUID();
return toIDString(u.getMostSignificantBits()) + toIDString(u.getLeastSignificantBits());
}
private static String toIDString(long i) {
char[] buf = new char[32];
int z = 64; // 1 << 6;
int cp = 32;
long b = z - 1;
do {
buf[--cp] = DIGITS66[(int)(i & b)];
i >>>= 6;
} while (i != 0);
return new String(buf, cp, (32-cp));
}
// array de 64+2 digitos
private final static char[] DIGITS66 = {
'0','1','2','3','4','5','6','7','8','9', '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',
'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',
'-','.','_','~'
};
}
我们可以使用UUID在java中创建一个唯一的ID，并在randomUUID()上调用类似UUID的方法。
String uniqueID = UUID.randomUUID().toString();
这将生成随机uniqueID，其返回类型将为String。
在java中有三种生成唯一ID的方法。
1）UUID类提供了一种生成唯一ID的简单方法。
UUID id = UUID.randomUUID();
System.out.println(id);
2）SecureRandom和MessageDigest
//initialization of the application
SecureRandom prng = SecureRandom.getInstance("SHA1PRNG");
//generate a random number
String randomNum = new Integer(prng.nextInt()).toString();
//get its digest
MessageDigest sha = MessageDigest.getInstance("SHA-1");
byte[] result = sha.digest(randomNum.getBytes());
System.out.println("Random number: " + randomNum);
System.out.println("Message digest: " + new String(result));
3）使用java.rmi.server.UID
UID userId = new UID();
System.out.println("userId: " + userId);