[iotdb] branch master updated: Optimize the implementation of singleton (#3585)

[ha...@apache.org]

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haonan pushed a commit to branch master
in repository https://gitbox.apache.org/repos/asf/iotdb.git


The following commit(s) were added to refs/heads/master by this push:
     new 56ea509  Optimize the implementation of singleton (#3585)
56ea509 is described below

commit 56ea509d863a54ff7a9f77a6972ec23e5df3d7dd
Author: limeng <li...@live.cn>
AuthorDate: Fri Jul 16 13:27:19 2021 +0800

    Optimize the implementation of singleton (#3585)
    
    Co-authored-by: limeng32 <li...@yonyou.com>
---
 .../java/org/apache/iotdb/db/rescon/TVListAllocator.java     | 12 ++++++++----
 .../main/java/org/apache/iotdb/db/service/UpgradeSevice.java |  9 +++++++--
 2 files changed, 15 insertions(+), 6 deletions(-)

diff --git a/server/src/main/java/org/apache/iotdb/db/rescon/TVListAllocator.java b/server/src/main/java/org/apache/iotdb/db/rescon/TVListAllocator.java
index b90c33e..f2e54ab 100644
--- a/server/src/main/java/org/apache/iotdb/db/rescon/TVListAllocator.java
+++ b/server/src/main/java/org/apache/iotdb/db/rescon/TVListAllocator.java
@@ -40,10 +40,14 @@ public class TVListAllocator implements TVListAllocatorMBean, IService {
       String.format(
           "%s:%s=%s", IoTDBConstant.IOTDB_PACKAGE, IoTDBConstant.JMX_TYPE, getID().getJmxName());
 
-  private static final TVListAllocator INSTANCE = new TVListAllocator();
-
   public static TVListAllocator getInstance() {
-    return INSTANCE;
+    return InstanceHolder.INSTANCE;
+  }
+
+  private static class InstanceHolder {
+    private static final TVListAllocator INSTANCE = new TVListAllocator();
+
+    private InstanceHolder() {}
   }
 
   public synchronized TVList allocate(TSDataType dataType) {
@@ -84,7 +88,7 @@ public class TVListAllocator implements TVListAllocatorMBean, IService {
   @Override
   public void start() throws StartupException {
     try {
-      JMXService.registerMBean(INSTANCE, mbeanName);
+      JMXService.registerMBean(InstanceHolder.INSTANCE, mbeanName);
     } catch (Exception e) {
       throw new StartupException(this.getID().getName(), e.getMessage());
     }
diff --git a/server/src/main/java/org/apache/iotdb/db/service/UpgradeSevice.java b/server/src/main/java/org/apache/iotdb/db/service/UpgradeSevice.java
index df1c394..4468208 100644
--- a/server/src/main/java/org/apache/iotdb/db/service/UpgradeSevice.java
+++ b/server/src/main/java/org/apache/iotdb/db/service/UpgradeSevice.java
@@ -36,7 +36,6 @@ public class UpgradeSevice implements IService {
 
   private static final Logger logger = LoggerFactory.getLogger(UpgradeSevice.class);
 
-  private static final UpgradeSevice INSTANCE = new UpgradeSevice();
   private ExecutorService upgradeThreadPool;
   private AtomicInteger threadCnt = new AtomicInteger();
   private static int cntUpgradeFileNum;
@@ -44,7 +43,13 @@ public class UpgradeSevice implements IService {
   private UpgradeSevice() {}
 
   public static UpgradeSevice getINSTANCE() {
-    return INSTANCE;
+    return InstanceHolder.INSTANCE;
+  }
+
+  public static class InstanceHolder {
+    private static final UpgradeSevice INSTANCE = new UpgradeSevice();
+
+    private InstanceHolder() {}
   }
 
   @Override