blocks|key|41034|text|创建一个UUID。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|41035|String+uniqueID+=+UUID.randomUUID().toString();|code-block|syntax|javascript|41036|entityMap|0|LINK|mutability|MUTABLE|url|http://docs.oracle.com/javase/8/docs/api/java/util/UUID.html^0|4|4|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@$A|R|B|S|1|T]]|C|$]]|$1|D|3|E|5|F|7|U|8|@]|9|@]|C|$G|H]]|$1|I|3|-4|5|6|7|V|8|@]|9|@]|C|$]]]|J|$K|$5|L|M|N|C|$O|P]]]]

Create a <a href="http://docs.oracle.com/javase/8/docs/api/java/util/UUID.html" rel="noreferrer">UUID</a>.

<pre><code>String uniqueID = UUID.randomUUID().toString();
</code></pre>

blocks|key|1445144|text|如果您想要简短的、人类可读的ID，并且只需要它们在每次JVM运行时都是唯一的：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1445145|private+static+long+idCounter+=+0;

public+static+synchronized+String+createID()
{
++++return+String.valueOf(idCounter%2B%2B);
}++++|code-block|syntax|javascript|1445146|编辑:注释中建议的替代方案-这依赖于线程安全的幕后“魔法”，但更具可扩展性，也同样安全：|offset|length|style|BOLD|1445147|private+static+AtomicLong+idCounter+=+new+AtomicLong();

public+static+String+createID()
{
++++return+String.valueOf(idCounter.getAndIncrement());
}|1445148|entityMap^0|0|0|0|9|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|R|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|S|8|@$I|T|J|U|K|L]]|9|@]|A|$]]|$1|M|3|N|5|D|7|V|8|@]|9|@]|A|$E|F]]|$1|O|3|-4|5|6|7|W|8|@]|9|@]|A|$]]]|P|$]]

If you want short, human-readable IDs and only need them to be unique per JVM run:

<pre><code>private static long idCounter = 0;

public static synchronized String createID()
{
 return String.valueOf(idCounter++);
} 
</code></pre>

Edit: Alternative suggested in the comments - this relies on under-the-hood "magic" for thread safety, but is more scalable and just as safe:

<pre><code>private static AtomicLong idCounter = new AtomicLong();

public static String createID()
{
 return String.valueOf(idCounter.getAndIncrement());
}
</code></pre>

blocks|key|1445082|text|java.util.UUID：toString()方法|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1445083|entityMap|0|LINK|mutability|MUTABLE|url|http://java.sun.com/javase/6/docs/api/java/util/UUID.html^0|0|E|0|E|0|0^^$0|@$1|2|3|4|5|6|7|N|8|@$9|O|A|P|B|C]]|D|@$9|Q|A|R|1|S]]|E|$]]|$1|F|3|-4|5|6|7|T|8|@]|D|@]|E|$]]]|G|$H|$5|I|J|K|E|$L|M]]]]

<a href="http://java.sun.com/javase/6/docs/api/java/util/UUID.html" rel="noreferrer"><code>java.util.UUID</code></a> : toString() method

blocks|key|41143|text|这就是我的价值所在:我之前实现了一个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的可读性(尽管很长)。以下是代码，以防它有任何用处：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|41144|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)+{
++++++%2B%2Bdiscriminator;
++++}+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("%25s-%25d-%25d-%25d",+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;+%2B%2Bi)+{
++++++System.err.println(fact.createId());
++++}
++}
}|code-block|syntax|javascript|41145|entityMap^0|I|9|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@$9|N|A|O|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|P|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|Q|8|@]|D|@]|E|$]]]|L|$]]

Here's my two cent's worth: I've previously implemented an <code>IdFactory</code> class that created IDs in the format [host name]-[application start time]-[current time]-[discriminator]. This largely guaranteed that IDs were unique across JVM instances whilst keeping the IDs readable (albeit quite long). Here's the code in case it's of any use:

<pre><code>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&lt;1000; ++i) {
 System.err.println(fact.createId());
 }
 }
}
</code></pre>

blocks|key|286123|text|使用Java生成唯一ID|type|unstyled|depth|inlineStyleRanges|entityRanges|data|286124|UUID是Java中生成唯一ID的最快、最简单的方法。|286125|import+java.util.UUID;

public+class+UniqueIDTest+{
++public+static+void+main(String[]+args)+{
++++UUID+uniqueKey+=+UUID.randomUUID();
++++System.out.println+(uniqueKey);
++}
}|code-block|syntax|javascript|286126|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|L|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|M|8|@]|9|@]|A|$G|H]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

Generate Unique ID Using Java
UUID is the fastest and easiest way to generate unique ID in Java.
<pre><code>import java.util.UUID;

public class UniqueIDTest {
 public static void main(String[] args) {
 UUID uniqueKey = UUID.randomUUID();
 System.out.println (uniqueKey);
 }
}
</code></pre>

blocks|key|286151|text|我为提供了一个优雅的解决方案，因为它是原生的，使用的代码更少。但是，如果您需要更短的ID，您可以使用此方法来缩短生成的字符串长度：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|286152|//+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())+%2B+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%2B2+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',
++++'-','.','_','~'
++};

}|code-block|syntax|javascript|286153|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

IMHO aperkins provided an an elegant solution cause is native and use less code.
But if you need a shorter ID you can use this approach to reduce the generated String length:

<pre><code>// 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 &lt;&lt; 6;
 int cp = 32;
 long b = z - 1;
 do {
 buf[--cp] = DIGITS66[(int)(i &amp; b)];
 i &gt;&gt;&gt;= 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',
 '-','.','_','~'
 };

}
</code></pre>

blocks|key|1588157|text|这增加了UUID生成的随机性，但确保每个生成的id的长度相同|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1588158|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+%2B+rand);
}|code-block|syntax|javascript|1588159|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

This adds a bit more randomness to the UUID generation but ensures each generated id is the same length

<pre><code>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);
}
</code></pre>

blocks|key|41350|text|我们可以使用UUID在java中创建一个唯一的ID，并像UUID上的randomUUID()一样调用该方法。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|41351|String+uniqueID+=+UUID.randomUUID().toString();|code-block|syntax|javascript|41352|这将生成返回类型为String的随机uniqueID。|41353|entityMap^0|6|4|S|4|Y|C|0|0|9|6|I|8|0^^$0|@$1|2|3|4|5|6|7|O|8|@$9|P|A|Q|B|C]|$9|R|A|S|B|C]|$9|T|A|U|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|V|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|W|8|@$9|X|A|Y|B|C]|$9|Z|A|10|B|C]]|D|@]|E|$]]|$1|M|3|-4|5|6|7|11|8|@]|D|@]|E|$]]]|N|$]]

We can create a unique ID in java by using the <code>UUID</code> and call the method like <code>randomUUID()</code> on <code>UUID</code>.

<pre><code>String uniqueID = UUID.randomUUID().toString();
</code></pre>

This will generate the random <code>uniqueID</code> whose return type will be <code>String</code>.

blocks|key|286190|text|在java中有三种方法来生成唯一id。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|286191|1)+UUID类提供了一种生成唯一ids的简单方法。|286192|+UUID+id+=+UUID.randomUUID();
+System.out.println(id);|code-block|syntax|javascript|286193|2)+SecureRandom和MessageDigest|286194|//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:+"+%2B+randomNum);
System.out.println("Message+digest:+"+%2B+new+String(result));|286195|3)使用java.rmi.server.UID|286196|UID+userId+=+new+UID();
System.out.println("userId:+"+%2B+userId);|286197|entityMap^0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|T|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|U|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|V|8|@]|9|@]|A|$]]|$1|K|3|L|5|F|7|W|8|@]|9|@]|A|$G|H]]|$1|M|3|N|5|6|7|X|8|@]|9|@]|A|$]]|$1|O|3|P|5|F|7|Y|8|@]|9|@]|A|$G|H]]|$1|Q|3|-4|5|6|7|Z|8|@]|9|@]|A|$]]]|R|$]]

There are three way to generate unique id in java.

1) the UUID class provides a simple means for generating unique ids.

<pre><code> UUID id = UUID.randomUUID();
 System.out.println(id);
</code></pre>

2) SecureRandom and MessageDigest

<pre><code>//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));
</code></pre>

3) using a java.rmi.server.UID

<pre><code>UID userId = new UID();
System.out.println("userId: " + userId);
</code></pre>

blocks|key|41424|text|带计数信息的唯一ID+|type|unstyled|depth|inlineStyleRanges|offset|length|style|BOLD|entityRanges|data|41425|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+%2B+"-"+%2B+currentCounter;
++++}
}|code-block|syntax|javascript|41426|entityMap^0|6|5|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@$9|N|A|O|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|P|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|Q|8|@]|D|@]|E|$]]]|L|$]]

Unique ID with count information

<pre><code>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;
 }
}
</code></pre>

blocks|key|1588183|text|String+name,password;

public+int+idGen()+{

++++int+id+=+this.name.hashCode()+%2B+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;
}|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|1588184|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code>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()&gt;Max_Length) 
 {
 id = (int) (id /Math.pow(10.0,length - Max_Length ));
 }
 return id;
}
</code></pre>

I'm looking for the best way to create a unique ID as a String in Java.

Any guidance appreciated, thanks.

I should mention I'm using Java 5.

How do I create a unique ID in Java?

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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我正在寻找在Java中将唯一ID创建为字符串的最佳方法。感谢您的指导，谢谢。我应该提一下我使用的是Java5。

问如何在Java中创建唯一ID？
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回答 11

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问如何在Java中创建唯一ID？EN

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问如何在Java中创建唯一ID？
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