yitter · tlanyan · Aug 17, 2025 · Aug 17, 2025
diff --git a/Java/source/src/main/java/com/github/yitter/contract/IdGeneratorOptions.java b/Java/source/src/main/java/com/github/yitter/contract/IdGeneratorOptions.java
@@ -19,6 +19,8 @@ public class IdGeneratorOptions {
     /**
      * 基础时间（ms单位）
      * 不能超过当前系统时间
+     * 默认值 1582136402000L，表示2020-02-20 00:00:02
+     * 新项目建议改成 1735689600000L，表示2025-01-01 00:00:00
      */
     public long BaseTime = 1582136402000L;
 
@@ -58,6 +60,12 @@ public class IdGeneratorOptions {
      */
     public short TopOverCostCount = 2000;
 
+    /**
+     * 时间精度： 0 毫秒  1 10毫秒(实际上是8毫秒)  2 100毫秒(实际上是128毫秒)  3 1秒(实际上是1024毫秒) 4 10秒(实际上是8192毫秒)
+     * 默认毫秒，与原版兼容
+     */
+    public short Precision = 0;
+
     public IdGeneratorOptions() {
 
     }

diff --git a/Java/source/src/main/java/com/github/yitter/core/SnowWorkerM1.java b/Java/source/src/main/java/com/github/yitter/core/SnowWorkerM1.java
@@ -14,40 +14,47 @@ public class SnowWorkerM1 implements ISnowWorker {
     /**
      * 基础时间
      */
-    protected final long BaseTime;
+    protected long BaseTime;
 
     /**
      * 机器码
      */
-    protected final short WorkerId;
+    protected short WorkerId;
 
     /**
      * 机器码位长
      */
-    protected final byte WorkerIdBitLength;
+    protected byte WorkerIdBitLength;
 
     /**
      * 自增序列数位长
      */
-    protected final byte SeqBitLength;
+    protected byte SeqBitLength;
 
     /**
      * 最大序列数（含）
      */
-    protected final int MaxSeqNumber;
+    protected int MaxSeqNumber;
 
     /**
      * 最小序列数（含）
      */
-    protected final short MinSeqNumber;
+    protected short MinSeqNumber;
 
     /**
      * 最大漂移次数（含）
      */
-    protected final int TopOverCostCount;
+    protected int TopOverCostCount;
 
-    protected final byte _TimestampShift;
-    protected final static byte[] _SyncLock = new byte[0];
+    /**
+     * 移位位数
+     */
+    protected int ShiftBits;
+
+    protected int _sleepTime;
+
+    protected byte _TimestampShift;
+    protected final byte[] _SyncLock = new byte[0];
 
     protected short _CurrentSeqNumber;
     protected long _LastTimeTick = 0;
@@ -61,15 +68,43 @@ public class SnowWorkerM1 implements ISnowWorker {
 
     public SnowWorkerM1(IdGeneratorOptions options) {
         BaseTime = options.BaseTime != 0 ? options.BaseTime : 1582136402000L;
-        WorkerIdBitLength = options.WorkerIdBitLength == 0 ? 6 : options.WorkerIdBitLength;
+        WorkerIdBitLength = options.WorkerIdBitLength;
         WorkerId = options.WorkerId;
         SeqBitLength = options.SeqBitLength == 0 ? 6 : options.SeqBitLength;
         MaxSeqNumber = options.MaxSeqNumber <= 0 ? (1 << SeqBitLength) - 1 : options.MaxSeqNumber;
         MinSeqNumber = options.MinSeqNumber;
         // TopOverCostCount = options.TopOverCostCount == 0 ? 2000 : options.TopOverCostCount;
         TopOverCostCount = options.TopOverCostCount;
+        switch (options.Precision) {
+            case 0:
+                ShiftBits = 0;
+                break;
+            case 1:
+                ShiftBits = 3;
+                break;
+            case 2:
+                ShiftBits = 7;
+                break;
+            case 3:
+                ShiftBits = 10;
+                break;
+            case 4:
+                ShiftBits = 13;
+                break;
+            default:
+                ShiftBits = 0;
+                break;
+        }
+        // 计算睡眠时间，最大1秒
+        _sleepTime = 1 << ShiftBits;
+        // 无需等到精度时间，分4次检查
+        if (_sleepTime > 50) {
+            _sleepTime = _sleepTime >> 2;
+        }
         _TimestampShift = (byte) (WorkerIdBitLength + SeqBitLength);
         _CurrentSeqNumber = MinSeqNumber;
+
+        BaseTime = BaseTime >> ShiftBits;
     }
 
     private void DoGenIdAction(OverCostActionArg arg) {
@@ -207,15 +242,15 @@ private long CalcTurnBackId(long useTimeTick) {
 
     protected long GetCurrentTimeTick() {
         long millis = System.currentTimeMillis();
-        return millis - BaseTime;
+        return (millis >> ShiftBits) - BaseTime;
     }
 
     protected long GetNextTimeTick() {
         long tempTimeTicker = GetCurrentTimeTick();
 
         while (tempTimeTicker <= _LastTimeTick) {
             try {
-                Thread.sleep(1);
+                Thread.sleep(_sleepTime);
             } catch (InterruptedException e) {
                 e.printStackTrace();
             }

diff --git a/Java/source/src/main/java/com/github/yitter/idgen/DefaultIdGenerator.java b/Java/source/src/main/java/com/github/yitter/idgen/DefaultIdGenerator.java
@@ -13,7 +13,7 @@
 
 public class DefaultIdGenerator implements IIdGenerator {
 
-    private static ISnowWorker _SnowWorker = null;
+    private ISnowWorker _SnowWorker = null;
 
     public DefaultIdGenerator(IdGeneratorOptions options) throws IdGeneratorException {
         if (options == null) {
@@ -26,19 +26,23 @@ public DefaultIdGenerator(IdGeneratorOptions options) throws IdGeneratorExceptio
         }
 
         // 2.WorkerIdBitLength
-        if (options.WorkerIdBitLength <= 0) {
-            throw new IdGeneratorException("WorkerIdBitLength error.(range:[1, 21])");
+        if (options.WorkerIdBitLength < 0) {
+            throw new IdGeneratorException("WorkerIdBitLength error.(range:[0, 21])");
         }
         if (options.WorkerIdBitLength + options.SeqBitLength > 22) {
             throw new IdGeneratorException("error：WorkerIdBitLength + SeqBitLength <= 22");
         }
 
         // 3.WorkerId
         int maxWorkerIdNumber = (1 << options.WorkerIdBitLength) - 1;
-        if (maxWorkerIdNumber == 0) {
-            maxWorkerIdNumber = 63;
+        // if (maxWorkerIdNumber == 0) {
+        //     maxWorkerIdNumber = 63;
+        // }
+        if (options.WorkerIdBitLength == 0 && options.WorkerId != 0) {
+            throw new IdGeneratorException(
+                    "WorkerIdBitLength is 0, WorkerId must be 0");
         }
-        if (options.WorkerId < 0 || options.WorkerId > maxWorkerIdNumber) {
+        else if (options.WorkerId < 0 || options.WorkerId > maxWorkerIdNumber) {
             throw new IdGeneratorException(
                     "WorkerId error. (range:[0, " + (maxWorkerIdNumber > 0 ? maxWorkerIdNumber : 63) + "]");
         }
@@ -62,6 +66,10 @@ public DefaultIdGenerator(IdGeneratorOptions options) throws IdGeneratorExceptio
             throw new IdGeneratorException("MinSeqNumber error. (range:[5, " + maxSeqNumber + "]");
         }
 
+        if (options.Precision < 0 || options.Precision > 4) {
+            throw new IdGeneratorException("Precision error. (range:[0, 4]");
+        }
+
         // 7.TopOverCostCount
         if (options.TopOverCostCount < 0 || options.TopOverCostCount > 10000) {
             throw new IdGeneratorException("TopOverCostCount error. (range:[0, 10000]");

diff --git a/Java/source/src/main/java/com/github/yitter/idgen/YitIdHelper.java b/Java/source/src/main/java/com/github/yitter/idgen/YitIdHelper.java
@@ -4,6 +4,9 @@
  */
 package com.github.yitter.idgen;
 
+import java.util.HashMap;
+import java.util.Map;
+
 import com.github.yitter.contract.IIdGenerator;
 import com.github.yitter.contract.IdGeneratorException;
 import com.github.yitter.contract.IdGeneratorOptions;
@@ -13,17 +16,34 @@
  */
 public class YitIdHelper {
 
-    private static IIdGenerator idGenInstance = null;
+    private static final String DEFAULT_INSTANCE_NAME = "default";
+
+    private static final Map<String, IIdGenerator> idGenInstanceMap = new HashMap<>();
 
     public static IIdGenerator getIdGenInstance() {
-        return idGenInstance;
+        return idGenInstanceMap.get(DEFAULT_INSTANCE_NAME);
+    }
+
+    public static IIdGenerator getIdGenInstance(String instanceName) {
+        return idGenInstanceMap.get(instanceName);
     }
 
     /**
      * 设置参数，建议程序初始化时执行一次
      */
     public static void setIdGenerator(IdGeneratorOptions options) throws IdGeneratorException {
-        idGenInstance = new DefaultIdGenerator(options);
+        idGenInstanceMap.put(DEFAULT_INSTANCE_NAME, new DefaultIdGenerator(options));
+    }
+
+    /**
+     * 设置参数，建议程序初始化时执行一次
+     */
+    public static void setIdGenerator(String instanceName, IdGeneratorOptions options) throws IdGeneratorException {
+        if (instanceName == null || instanceName.trim().isEmpty()) {
+            throw new IdGeneratorException("instanceName cannot be null or empty");
+        }
+
+        idGenInstanceMap.put(instanceName, new DefaultIdGenerator(options));
     }
 
     /**
@@ -37,9 +57,24 @@ public static long nextId() throws IdGeneratorException {
         // idGenInstance = new DefaultIdGenerator(new IdGeneratorOptions((short) 1));
         // }
 
-        if (idGenInstance == null)
+        var generator = idGenInstanceMap.get(DEFAULT_INSTANCE_NAME);
+        if (generator == null)
             throw new IdGeneratorException("Please initialize Yitter.IdGeneratorOptions first.");
 
-        return idGenInstance.newLong();
+        return generator.newLong();
+    }
+
+    /**
+     * 生成新的Id
+     * 调用本方法前，请确保调用了 SetIdGenerator 方法做初始化。
+     *
+     * @return
+     */
+    public static long nextId(String instanceName) throws IdGeneratorException {
+        var generator = idGenInstanceMap.get(instanceName);
+        if (generator == null)
+            throw new IdGeneratorException("Please initialize instance: " + instanceName + " with YitIdHelper.setIdGenerator(instanceName, options) first.");
+
+        return generator.newLong();
     }
 }
diff --git a/README.md b/README.md
@@ -1,5 +1,19 @@
 # 雪花算法中非常好用的数字ID生成器
 
+Java代码相对于原版做了如下改动，适用于中小型项目生成更短和数值更小的ID：
+
+1. 支持不同的时间精度，默认是1毫秒，与原版兼容；
+2. WorkIdBitLength支持为0，适用于单机版的小项目；
+3. 支持多个generator instance，服务于不同的场景
+
+与原版相比，改进版的ID长度最低可降低到9位，更有效的利用号段资源。
+
+关于改进的更多说明及程序结果可参考博文： [一个改进的Java短ID生成库](https://itlanyan.com/an-improved-short-id-generator/)
+
+
+------------- 以下是原版说明 --------------
+
+
 ## 💎 最佳实践（置顶）
 
 针对大家在使用中经常出现的性能疑问，我给出以下3组最佳实践：
@@ -101,7 +115,7 @@
  * +-------------------------+--------------+----------+
  * | 1.相对基础时间的时间差 | 2.WorkerId | 3.序列数 |
  * +-------------------------+--------------+----------+
- * 
+ *
  * 第1部分，时间差，是生成ID时的系统时间减去 BaseTime 的总时间差（毫秒单位）。
  * 第2部分，WorkerId，是区分不同机器或不同应用的唯一ID，最大值由 WorkerIdBitLength（默认6）限定。
  * 第3部分，序列数，是每毫秒下的序列数，由参数中的 SeqBitLength（默认6）限定。
@@ -242,20 +256,20 @@ extern void UnRegister();
 
 ## 已实现的语言
 
-| 语言 |  github  | 
-|  ----  | ----  |  
-| 🌲 C# | [查看示例][1]  | 
-| 🌲 Java | [查看示例][2]  | 
-| 🌲 Go| [查看示例][3]  | 
-| 🌲 Rust | [查看示例][4]  | 
-| 🌲 Python | [查看示例][10]  | 
+| 语言 |  github  |
+|  ----  | ----  |
+| 🌲 C# | [查看示例][1]  |
+| 🌲 Java | [查看示例][2]  |
+| 🌲 Go| [查看示例][3]  |
+| 🌲 Rust | [查看示例][4]  |
+| 🌲 Python | [查看示例][10]  |
 | 🌲 C | [查看示例][5]  |
 | 🌲 C (PHP扩展) | [查看示例][7]  |
 | 🌲 Delphi (Pascal) | [查看示例][6]  |
 | 🌲 JavaScript | [查看示例][8]  |
 | 🌲 TypeScript | [查看示例][9]  |
-| 🌲 V | [查看示例][6]  | 
-| 🌲 D | [查看示例][72]  | 
+| 🌲 V | [查看示例][6]  |
+| 🌲 D | [查看示例][72]  |
 
 
 ## 技术支持