blocks|key|892061|text|如果HD失败，您只需设置新的和未使用的2位服务器标识符，并确保该数字是唯一的(至少24小时)。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|892062|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

If HD fails you can just set new and unused 2 digit server identifier and be sure that the number is unique (for 24 hours at least)

blocks|key|977733|text|以下内容|type|unstyled|depth|inlineStyleRanges|entityRanges|data|977734|{XX}{dd}{HHmm}{N}|code-block|syntax|javascript|977735|其中{XX}是机器号{dd}是月份{HHmm}当前时间(24小时)的日期，{N}是顺序编号。|977736|一个hd崩溃将需要超过一分钟，所以从0开始再次不是一个问题。|977737|还可以根据需要将{dd}替换为{ss}数秒。每分钟的唯一性期与请求。|977738|entityMap^0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|Q|8|@]|9|@]|A|$]]|$1|I|3|J|5|6|7|R|8|@]|9|@]|A|$]]|$1|K|3|L|5|6|7|S|8|@]|9|@]|A|$]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

The Following 

<pre><code>{XX}{dd}{HHmm}{N}
</code></pre>

Where {XX} is the machine number {dd} is the day of the month {HHmm} current time (24hr) and {N} a sequential number.

A hd crash will take more than a minute so starting at 0 again is not a problem.

You can also replace {dd} with {ss} for seconds, depending on requirements. Uniqueness period vs. requests per minute.

blocks|key|891999|text|如何生成GUID+(确保唯一性)，然后使用某种哈希函数将GUID转换为9位数字？|type|unstyled|depth|inlineStyleRanges|entityRanges|data|892000|就在我头顶上..。|892001|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|F|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|G|8|@]|9|@]|A|$]]|$1|D|3|-4|5|6|7|H|8|@]|9|@]|A|$]]]|E|$]]

How about generating GUIDs (ensures uniqueness) and then using some sort of hash function to turn the GUID into a 9-digit number? 
Just off the top of my head...

blocks|key|977148|text|在以下方面使用一种变体：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|977149|md5(uniqid(rand(),+true));|code-block|syntax|javascript|977150|这只是个想法。|977151|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

Use a variation on:

<pre><code>md5(uniqid(rand(), true));
</code></pre>

Just a thought.

blocks|key|977756|text|在我最近的项目中，我也遇到了这样的要求，即在没有任何数据库的情况下生成N位长序列号。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|977757|这实际上是一个很好的面试问题，因为在性能和软件崩溃恢复方面都有考虑。进一步阅读如果有兴趣的话。|offset|length|977758|以下代码具有以下特性：|977759|在每个序列前加上一个前缀。|ordered-list-item|977760|序列缓存就像Oracle序列一样。|977761|最重要的是，有从软件崩溃中恢复序列的恢复逻辑。|977762|附件：|977763|import+java.util.concurrent.atomic.AtomicLong;
import+org.apache.commons.lang.StringUtils;

/**
+*+This+is+a+customized+Sequence+Generator+which+simulates+Oracle+DB+Sequence+Generator.+However+the+master+sequence
+*+is+stored+locally+in+the+file+as+there+is+no+access+to+Oracle+database.+The+output+format+is+"prefix"+%2B+number.
+*+
+*+Sample+output: 
+*+1.+FixLengthIDSequence(null,null,15,0,99,0)+will+generate+15,+16,+...+99,+00 
+*+2.+FixLengthIDSequence(null,"K",1,1,99,0)+will+generate+K01,+K02,+...+K99,+K01 
+*+3.+FixLengthIDSequence(null,"SG",100,2,9999,100)+will+generate+SG0100,+SG0101,+...+SG8057,+(in+case+server+crashes,+the+new+init+value+will+start+from+last+cache+value%2B1)+SG8101,+...+SG9999,+SG0002 
+*/
public+final+class+FixLengthIDSequence+{

++++private+static+String+FNAME;
++++private+static+String+PREFIX;
++++private+static+AtomicLong+SEQ_ID;
++++private+static+long+MINVALUE;
++++private+static+long+MAXVALUE;
++++private+static+long+CACHEVALUE;

++++//+some+internal+working+values.
++++private+int+iMaxLength;+//+max+numeric+length+excluding+prefix,+for+left+padding+zeros.
++++private+long+lNextSnapshot;+//+to+keep+track+of+when+to+update+sequence+value+to+file.+
++++private+static+boolean+bInit+=+false;+//+to+enable+ShutdownHook+routine+after+program+has+properly+initialized

++++static+{
++++++++//+Inspiration+from+http://stackoverflow.com/questions/22416826/sequence-generator-in-java-for-unique-id#35697336.
++++++++Runtime.getRuntime().addShutdownHook(new+Thread(()+->+{
++++++++++++if+(bInit)+{+//+Without+this,+saveToLocal+may+hit+NullPointerException.
++++++++++++++++saveToLocal(SEQ_ID.longValue());
++++++++++++}
++++++++}));
++++}

++++/**
+++++*+This+POJO+style+constructor+should+be+initialized+via+Spring+Singleton.+Otherwise,+rewrite+this+constructor+into+Singleton+design+pattern.
+++++*+
+++++*+@param+sFilename+This+is+the+absolute+file+path+to+store+the+sequence+number.+To+reset+the+sequence,+this+file+needs+to+be+removed+manually.
+++++*+@param+prefix+The+hard-coded+identifier.
+++++*+@param+initvalue
+++++*+@param+minvalue
+++++*+@param+maxvalue
+++++*+@param+cache
+++++*+@throws+Exception
+++++*/
++++public+FixLengthIDSequence(String+sFilename,+String+prefix,+long+initvalue,+long+minvalue,+long+maxvalue,+int+cache)+throws+Exception+{
++++++++bInit+=+false;
++++++++FNAME+=+(sFilename==null)?"C:\\Temp\\sequence.txt":sFilename;
++++++++PREFIX+=+(prefix==null)?"":prefix;
++++++++SEQ_ID+=+new+AtomicLong(initvalue);
++++++++MINVALUE+=+minvalue;
++++++++MAXVALUE+=+maxvalue;+iMaxLength+=+Long.toString(MAXVALUE).length();
++++++++CACHEVALUE+=+(cache+<=+0)?1:cache;+lNextSnapshot+=+roundUpNumberByMultipleValue(initvalue,+cache);+//+Internal+cache+is+always+1,+equals+no+cache.

++++++++//+If+sequence+file+exists+and+valid,+restore+the+saved+sequence.
++++++++java.io.File+f+=+new+java.io.File(FNAME);
++++++++if+(f.exists())+{
++++++++++++String[]+saSavedSequence+=+loadToString().split(",");
++++++++++++if+(saSavedSequence.length+!=+6)+{
++++++++++++++++throw+new+Exception("Local+Sequence+file+is+not+valid");
++++++++++++}

++++++++++++PREFIX+=+saSavedSequence[0];
++++++++++++//SEQ_ID+=+new+AtomicLong(Long.parseLong(saSavedSequence[1]));+//+savedInitValue
++++++++++++MINVALUE+=+Long.parseLong(saSavedSequence[2]);
++++++++++++MAXVALUE+=+Long.parseLong(saSavedSequence[3]);+iMaxLength+=+Long.toString(MAXVALUE).length();
++++++++++++CACHEVALUE+=+Long.parseLong(saSavedSequence[4]);
++++++++++++lNextSnapshot+=+Long.parseLong(saSavedSequence[5]);

++++++++++++//+For+sequence+number+recovery
++++++++++++//+The+rule+to+determine+to+continue+using+SEQ_ID+or+lNextSnapshot+as+subsequent+sequence+number:
++++++++++++//+If+savedInitValue+=+savedSnapshot,+it+was+saved+by+ShutdownHook+->+use+SEQ_ID.
++++++++++++//+Else+if+saveInitValue+<+savedSnapshot,+it+was+saved+by+periodic+Snapshot+->+use+lNextSnapshot%2B1.
++++++++++++if+(saSavedSequence[1].equals(saSavedSequence[5]))+{
++++++++++++++++long+previousSEQ+=+Long.parseLong(saSavedSequence[1]);
++++++++++++++++SEQ_ID+=+new+AtomicLong(previousSEQ);
++++++++++++++++lNextSnapshot+=+roundUpNumberByMultipleValue(previousSEQ,CACHEVALUE);
++++++++++++}+else+{
++++++++++++++++SEQ_ID+=+new+AtomicLong(lNextSnapshot%2B1);+//+SEQ_ID+starts+fresh+from+lNextSnapshot%2B!.
++++++++++++++++lNextSnapshot+=+roundUpNumberByMultipleValue(SEQ_ID.longValue(),CACHEVALUE);
++++++++++++}
++++++++}

++++++++//+Catch+invalid+values.
++++++++if+(minvalue+<+0)+{
++++++++++++throw+new+Exception("MINVALUE+cannot+be+less+than+0");
++++++++}
++++++++if+(maxvalue+<+0)+{
++++++++++++throw+new+Exception("MAXVALUE+cannot+be+less+than+0");
++++++++}
++++++++if+(minvalue+>=+maxvalue)+{
++++++++++++throw+new+Exception("MINVALUE+cannot+be+greater+than+MAXVALUE");
++++++++}
++++++++if+(cache+>=+maxvalue)+{
++++++++++++throw+new+Exception("CACHE+value+cannot+be+greater+than+MAXVALUE");
++++++++}

++++++++//+Save+the+next+Snapshot.
++++++++saveToLocal(lNextSnapshot);
++++++++bInit+=+true;
++++}

++++/**
+++++*+Equivalent+to+Oracle+Sequence+nextval.
+++++*+@return+String+because+Next+Value+is+usually+left+padded+with+zeros,+e.g.+"00001".
+++++*/
++++public+String+nextVal()+{
++++++++if+(SEQ_ID.longValue()+>+MAXVALUE)+{
++++++++++++SEQ_ID.set(MINVALUE);
++++++++++++lNextSnapshot+=+roundUpNumberByMultipleValue(MINVALUE,CACHEVALUE);
++++++++}

++++++++if+(SEQ_ID.longValue()+>+lNextSnapshot)+{
++++++++++++lNextSnapshot+=+roundUpNumberByMultipleValue(lNextSnapshot,CACHEVALUE);
++++++++++++saveToLocal(lNextSnapshot);
++++++++}

++++++++return+PREFIX.concat(StringUtils.leftPad(Long.toString(SEQ_ID.getAndIncrement()),iMaxLength,"0"));
++++}

++++/**
+++++*+Store+sequence+value+into+the+local+file.+This+routine+is+called+either+by+Snapshot+or+ShutdownHook+routines. 
+++++*+If+called+by+Snapshot,+currentCount+==+Snapshot. 
+++++*+If+called+by+ShutdownHook,+currentCount+==+current+SEQ_ID.
+++++*+@param+currentCount+-+This+value+is+inserted+by+either+Snapshot+or+ShutdownHook+routines.
+++++*/
++++private+static+void+saveToLocal+(long+currentCount)+{
++++++++try+(java.io.Writer+w+=+new+java.io.BufferedWriter(new+java.io.OutputStreamWriter(new+java.io.FileOutputStream(FNAME),+"utf-8")))+{
++++++++++++w.write(PREFIX+%2B+","+%2B+SEQ_ID.longValue()+%2B+","+%2B+MINVALUE+%2B+","+%2B+MAXVALUE+%2B+","+%2B+CACHEVALUE+%2B+","+%2B+currentCount);
++++++++++++w.flush();
++++++++}+catch+(Exception+e)+{
++++++++++++e.printStackTrace();
++++++++}
++++}

++++/**
+++++*+Load+the+sequence+file+content+into+String.
+++++*+@return
+++++*/
++++private+String+loadToString()+{
++++++++try+{
++++++++++++return+new+String(java.nio.file.Files.readAllBytes(java.nio.file.Paths.get(FNAME)));
++++++++}+catch+(Exception+e)+{
++++++++++++e.printStackTrace();
++++++++}
++++++++return+"";
++++}

++++/**
+++++*+Utility+method+to+round+up+num+to+next+multiple+value.+This+method+is+used+to+calculate+the+next+cache+value.
+++++*+
+++++*+(Reference:+http://stackoverflow.com/questions/18407634/rounding-up-to-the-nearest-hundred)
+++++*+
+++++*+Sample+output:
+++++*+<pre>
+++++*+System.out.println(roundUpNumberByMultipleValue(9,10));+=+10
+++++*+System.out.println(roundUpNumberByMultipleValue(10,10));+=+20
+++++*+System.out.println(roundUpNumberByMultipleValue(19,10));+=+20
+++++*+System.out.println(roundUpNumberByMultipleValue(100,10));+=+110
+++++*+System.out.println(roundUpNumberByMultipleValue(109,10));+=+110
+++++*+System.out.println(roundUpNumberByMultipleValue(110,10));+=+120
+++++*+System.out.println(roundUpNumberByMultipleValue(119,10));+=+120
+++++*+</pre>
+++++*+
+++++*+@param+num+Value+must+be+greater+and+equals+to+positive+integer+1.
+++++*+@param+multiple+Value+must+be+greater+and+equals+to+positive+integer+1.
+++++*+@return
+++++*/
++++private+long+roundUpNumberByMultipleValue(long+num,+long+multiple)+{
++++++++if+(num<=0)+num=1;
++++++++if+(multiple<=0)+multiple=1;
++++++++if+(num+%25+multiple+!=+0)+{
++++++++++++long+division+=+(long)+((num+/+multiple)+%2B+1);
++++++++++++return+division+*+multiple;
++++++++}+else+{
++++++++++++return+num+%2B+multiple;
++++++++}
++++}

++++/**
+++++*+Main+method+for+testing+purpose.
+++++*+@param+args
+++++*/
++++public+static+void+main(String[]+args)+throws+Exception+{
++++++++//FixLengthIDSequence(Filename,+prefix,+initvalue,+minvalue,+maxvalue,+cache)
++++++++FixLengthIDSequence+seq+=+new+FixLengthIDSequence(null,"H",50,1,999,10);
++++++++for+(int+i=0;+i<12;+i%2B%2B)+{
++++++++++++System.out.println(seq.nextVal());
++++++++++++Thread.sleep(1000);
++++++++++++//if+(i==8)+{+System.exit(0);+}
++++++++}
++++}

}|code-block|syntax|javascript|977764|要测试代码，让序列正常运行。您可以按Ctrl%2BC来模拟服务器崩溃。下一个序列号将从NextSnapshot%2B1继续。|977765|entityMap|0|LINK|mutability|MUTABLE|url|http://oraclesoon.blogspot.sg/2017/02/java-sequence-generator-which-simulates.html^0|0|Y|5|0|0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|15|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|16|8|@]|9|@$D|17|E|18|1|19]]|A|$]]|$1|F|3|G|5|6|7|1A|8|@]|9|@]|A|$]]|$1|H|3|I|5|J|7|1B|8|@]|9|@]|A|$]]|$1|K|3|L|5|J|7|1C|8|@]|9|@]|A|$]]|$1|M|3|N|5|J|7|1D|8|@]|9|@]|A|$]]|$1|O|3|P|5|6|7|1E|8|@]|9|@]|A|$]]|$1|Q|3|R|5|S|7|1F|8|@]|9|@]|A|$T|U]]|$1|V|3|W|5|6|7|1G|8|@]|9|@]|A|$]]|$1|X|3|-4|5|6|7|1H|8|@]|9|@]|A|$]]]|Y|$Z|$5|10|11|12|A|$13|14]]]]

In my recent project I also come across this requirement, to generate N digit long sequence number without any database.

This is actually a good Interview question, because there are consideration on performance and software crash recovery. <a href="http://oraclesoon.blogspot.sg/2017/02/java-sequence-generator-which-simulates.html" rel="nofollow noreferrer">Further Reading</a> if interested.

The following code has these features:

<ol>
<li>Prefix each sequence with a prefix.</li>
<li>Sequence cache like Oracle Sequence.</li>
<li>Most importantly, there is recovery logic to resume sequence from software crash.</li>
</ol>

Complete implementation attached:

<pre><code>import java.util.concurrent.atomic.AtomicLong;
import org.apache.commons.lang.StringUtils;

/**
 * This is a customized Sequence Generator which simulates Oracle DB Sequence Generator. However the master sequence
 * is stored locally in the file as there is no access to Oracle database. The output format is "prefix" + number.
 * &lt;p&gt;
 * &lt;u&gt;&lt;b&gt;Sample output:&lt;/u&gt;&lt;/b&gt;&lt;br&gt;
 * 1. FixLengthIDSequence(null,null,15,0,99,0) will generate 15, 16, ... 99, 00&lt;br&gt;
 * 2. FixLengthIDSequence(null,"K",1,1,99,0) will generate K01, K02, ... K99, K01&lt;br&gt;
 * 3. FixLengthIDSequence(null,"SG",100,2,9999,100) will generate SG0100, SG0101, ... SG8057, (in case server crashes, the new init value will start from last cache value+1) SG8101, ... SG9999, SG0002&lt;br&gt;
 */
public final class FixLengthIDSequence {

 private static String FNAME;
 private static String PREFIX;
 private static AtomicLong SEQ_ID;
 private static long MINVALUE;
 private static long MAXVALUE;
 private static long CACHEVALUE;

 // some internal working values.
 private int iMaxLength; // max numeric length excluding prefix, for left padding zeros.
 private long lNextSnapshot; // to keep track of when to update sequence value to file. 
 private static boolean bInit = false; // to enable ShutdownHook routine after program has properly initialized

 static {
 // Inspiration from http://stackoverflow.com/questions/22416826/sequence-generator-in-java-for-unique-id#35697336.
 Runtime.getRuntime().addShutdownHook(new Thread(() -&gt; {
 if (bInit) { // Without this, saveToLocal may hit NullPointerException.
 saveToLocal(SEQ_ID.longValue());
 }
 }));
 }

 /**
 * This POJO style constructor should be initialized via Spring Singleton. Otherwise, rewrite this constructor into Singleton design pattern.
 * 
 * @param sFilename This is the absolute file path to store the sequence number. To reset the sequence, this file needs to be removed manually.
 * @param prefix The hard-coded identifier.
 * @param initvalue
 * @param minvalue
 * @param maxvalue
 * @param cache
 * @throws Exception
 */
 public FixLengthIDSequence(String sFilename, String prefix, long initvalue, long minvalue, long maxvalue, int cache) throws Exception {
 bInit = false;
 FNAME = (sFilename==null)?"C:\\Temp\\sequence.txt":sFilename;
 PREFIX = (prefix==null)?"":prefix;
 SEQ_ID = new AtomicLong(initvalue);
 MINVALUE = minvalue;
 MAXVALUE = maxvalue; iMaxLength = Long.toString(MAXVALUE).length();
 CACHEVALUE = (cache &lt;= 0)?1:cache; lNextSnapshot = roundUpNumberByMultipleValue(initvalue, cache); // Internal cache is always 1, equals no cache.

 // If sequence file exists and valid, restore the saved sequence.
 java.io.File f = new java.io.File(FNAME);
 if (f.exists()) {
 String[] saSavedSequence = loadToString().split(",");
 if (saSavedSequence.length != 6) {
 throw new Exception("Local Sequence file is not valid");
 }

 PREFIX = saSavedSequence[0];
 //SEQ_ID = new AtomicLong(Long.parseLong(saSavedSequence[1])); // savedInitValue
 MINVALUE = Long.parseLong(saSavedSequence[2]);
 MAXVALUE = Long.parseLong(saSavedSequence[3]); iMaxLength = Long.toString(MAXVALUE).length();
 CACHEVALUE = Long.parseLong(saSavedSequence[4]);
 lNextSnapshot = Long.parseLong(saSavedSequence[5]);

 // For sequence number recovery
 // The rule to determine to continue using SEQ_ID or lNextSnapshot as subsequent sequence number:
 // If savedInitValue = savedSnapshot, it was saved by ShutdownHook -&gt; use SEQ_ID.
 // Else if saveInitValue &lt; savedSnapshot, it was saved by periodic Snapshot -&gt; use lNextSnapshot+1.
 if (saSavedSequence[1].equals(saSavedSequence[5])) {
 long previousSEQ = Long.parseLong(saSavedSequence[1]);
 SEQ_ID = new AtomicLong(previousSEQ);
 lNextSnapshot = roundUpNumberByMultipleValue(previousSEQ,CACHEVALUE);
 } else {
 SEQ_ID = new AtomicLong(lNextSnapshot+1); // SEQ_ID starts fresh from lNextSnapshot+!.
 lNextSnapshot = roundUpNumberByMultipleValue(SEQ_ID.longValue(),CACHEVALUE);
 }
 }

 // Catch invalid values.
 if (minvalue &lt; 0) {
 throw new Exception("MINVALUE cannot be less than 0");
 }
 if (maxvalue &lt; 0) {
 throw new Exception("MAXVALUE cannot be less than 0");
 }
 if (minvalue &gt;= maxvalue) {
 throw new Exception("MINVALUE cannot be greater than MAXVALUE");
 }
 if (cache &gt;= maxvalue) {
 throw new Exception("CACHE value cannot be greater than MAXVALUE");
 }

 // Save the next Snapshot.
 saveToLocal(lNextSnapshot);
 bInit = true;
 }

 /**
 * Equivalent to Oracle Sequence nextval.
 * @return String because Next Value is usually left padded with zeros, e.g. "00001".
 */
 public String nextVal() {
 if (SEQ_ID.longValue() &gt; MAXVALUE) {
 SEQ_ID.set(MINVALUE);
 lNextSnapshot = roundUpNumberByMultipleValue(MINVALUE,CACHEVALUE);
 }

 if (SEQ_ID.longValue() &gt; lNextSnapshot) {
 lNextSnapshot = roundUpNumberByMultipleValue(lNextSnapshot,CACHEVALUE);
 saveToLocal(lNextSnapshot);
 }

 return PREFIX.concat(StringUtils.leftPad(Long.toString(SEQ_ID.getAndIncrement()),iMaxLength,"0"));
 }

 /**
 * Store sequence value into the local file. This routine is called either by Snapshot or ShutdownHook routines.&lt;br&gt;
 * If called by Snapshot, currentCount == Snapshot.&lt;br&gt;
 * If called by ShutdownHook, currentCount == current SEQ_ID.
 * @param currentCount - This value is inserted by either Snapshot or ShutdownHook routines.
 */
 private static void saveToLocal (long currentCount) {
 try (java.io.Writer w = new java.io.BufferedWriter(new java.io.OutputStreamWriter(new java.io.FileOutputStream(FNAME), "utf-8"))) {
 w.write(PREFIX + "," + SEQ_ID.longValue() + "," + MINVALUE + "," + MAXVALUE + "," + CACHEVALUE + "," + currentCount);
 w.flush();
 } catch (Exception e) {
 e.printStackTrace();
 }
 }

 /**
 * Load the sequence file content into String.
 * @return
 */
 private String loadToString() {
 try {
 return new String(java.nio.file.Files.readAllBytes(java.nio.file.Paths.get(FNAME)));
 } catch (Exception e) {
 e.printStackTrace();
 }
 return "";
 }

 /**
 * Utility method to round up num to next multiple value. This method is used to calculate the next cache value.
 * &lt;p&gt;
 * (Reference: http://stackoverflow.com/questions/18407634/rounding-up-to-the-nearest-hundred)
 * &lt;p&gt;
 * &lt;u&gt;&lt;b&gt;Sample output:&lt;/b&gt;&lt;/u&gt;
 * &lt;pre&gt;
 * System.out.println(roundUpNumberByMultipleValue(9,10)); = 10
 * System.out.println(roundUpNumberByMultipleValue(10,10)); = 20
 * System.out.println(roundUpNumberByMultipleValue(19,10)); = 20
 * System.out.println(roundUpNumberByMultipleValue(100,10)); = 110
 * System.out.println(roundUpNumberByMultipleValue(109,10)); = 110
 * System.out.println(roundUpNumberByMultipleValue(110,10)); = 120
 * System.out.println(roundUpNumberByMultipleValue(119,10)); = 120
 * &lt;/pre&gt;
 * 
 * @param num Value must be greater and equals to positive integer 1.
 * @param multiple Value must be greater and equals to positive integer 1.
 * @return
 */
 private long roundUpNumberByMultipleValue(long num, long multiple) {
 if (num&lt;=0) num=1;
 if (multiple&lt;=0) multiple=1;
 if (num % multiple != 0) {
 long division = (long) ((num / multiple) + 1);
 return division * multiple;
 } else {
 return num + multiple;
 }
 }

 /**
 * Main method for testing purpose.
 * @param args
 */
 public static void main(String[] args) throws Exception {
 //FixLengthIDSequence(Filename, prefix, initvalue, minvalue, maxvalue, cache)
 FixLengthIDSequence seq = new FixLengthIDSequence(null,"H",50,1,999,10);
 for (int i=0; i&lt;12; i++) {
 System.out.println(seq.nextVal());
 Thread.sleep(1000);
 //if (i==8) { System.exit(0); }
 }
 }

}
</code></pre>

To test the code, let the sequence run normally. You can press Ctrl+C to simulate the server crash. The next sequence number will continue from NextSnapshot+1.

blocks|key|2418047|text|使用其他唯一数据来源的前9位数字，如：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2418048|随机数|ordered-list-item|2418049|系统时间|2418050|正常运行时间|2418051|经过两秒钟的讨论，没有一个是唯一的，但是您可以使用它们作为哈希函数的种子值，就像在另一个答案中所建议的那样。|2418052|entityMap^0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$]]|$1|E|3|F|5|D|7|O|8|@]|9|@]|A|$]]|$1|G|3|H|5|D|7|P|8|@]|9|@]|A|$]]|$1|I|3|J|5|6|7|Q|8|@]|9|@]|A|$]]|$1|K|3|-4|5|6|7|R|8|@]|9|@]|A|$]]]|L|$]]

Cold you use the first 9 digits of some other source of unique data like:

<ol>
<li>a random number </li>
<li>System Time</li>
<li>Uptime</li>
</ol>

Having thaught about it for two seconds, none of those are unique on there own but you could use them as seed values for hash functions as was suggested in another answer.

I'd like to create 9-digit numeric ids that are unique across machines. I'm currently using a database sequence for this, but am wondering if it could be done without one. The sequences will be used for X12 EDI transactions, so they don't have to be unique forever. Maybe even only unique for 24 hours.

My only idea:

<ol>
<li>Each server has a 2 digit server identifier.</li>
<li>Each server maintains a file that essentially keeps track of a local sequence.</li>
<li>id = + &lt;7 digit sequence which wraps></li>
</ol>

My biggest problem with this is what to do if the hard-drive fails. I wouldn't know where it left off.

All of my other ideas essentially end up re-creating a centralized database sequence.

Any thoughts?

generating 9 digit ids without database sequence

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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我想要创建9位数字的数字‘d，在不同的机器上是独一无二的。我目前正在使用数据库序列，但我想知道是否可以不使用数据库序列。序列将用于X12 EDI事务，因此它们不必永远是唯一的。也许只有24小时是独一无二的。我唯一的想法是：每个服务器都有一个2位的服务器标识符。每个服务器都维护一个基本上跟踪本地序列的文件。id =+ <7位数列wraps>我最大的问题是如果硬盘坏了该怎么办。我不知道它停在哪里了。我

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