[SCB-2599] fix some singleton classes construction method not private (#3120)

diff --git a/huawei-cloud/dashboard/src/main/java/org/apache/servicecomb/huaweicloud/dashboard/monitor/data/CPUMonitorCalc.java b/huawei-cloud/dashboard/src/main/java/org/apache/servicecomb/huaweicloud/dashboard/monitor/data/CPUMonitorCalc.java
index 8c59ec3..6db0a85 100644
--- a/huawei-cloud/dashboard/src/main/java/org/apache/servicecomb/huaweicloud/dashboard/monitor/data/CPUMonitorCalc.java
+++ b/huawei-cloud/dashboard/src/main/java/org/apache/servicecomb/huaweicloud/dashboard/monitor/data/CPUMonitorCalc.java
@@ -35,7 +35,7 @@
 
   private long preUsedTime = 0;
 
-  public CPUMonitorCalc() {
+  private CPUMonitorCalc() {
     osMxBean = ManagementFactory.getOperatingSystemMXBean();
     threadMXBean = ManagementFactory.getThreadMXBean();
   }
diff --git a/service-registry/registry-local/src/main/java/org/apache/servicecomb/localregistry/LocalRegistryStore.java b/service-registry/registry-local/src/main/java/org/apache/servicecomb/localregistry/LocalRegistryStore.java
index b0ab959..1dfc9fd 100644
--- a/service-registry/registry-local/src/main/java/org/apache/servicecomb/localregistry/LocalRegistryStore.java
+++ b/service-registry/registry-local/src/main/java/org/apache/servicecomb/localregistry/LocalRegistryStore.java
@@ -60,7 +60,7 @@
   // second key is instance id
   private final Map<String, Map<String, MicroserviceInstance>> microserviceInstanceMap = new ConcurrentHashMap<>();
 
-  public LocalRegistryStore() {
+  private LocalRegistryStore() {
 
   }
 
diff --git a/service-registry/registry-service-center/src/main/java/org/apache/servicecomb/serviceregistry/adapter/EnvAdapterManager.java b/service-registry/registry-service-center/src/main/java/org/apache/servicecomb/serviceregistry/adapter/EnvAdapterManager.java
index 55949dc..c744383 100644
--- a/service-registry/registry-service-center/src/main/java/org/apache/servicecomb/serviceregistry/adapter/EnvAdapterManager.java
+++ b/service-registry/registry-service-center/src/main/java/org/apache/servicecomb/serviceregistry/adapter/EnvAdapterManager.java
@@ -35,7 +35,7 @@
 
   public static final EnvAdapterManager INSTANCE = new EnvAdapterManager();
 
-  public EnvAdapterManager() {
+  private EnvAdapterManager() {
     super(NAME);
     ENV_ADAPTERS.forEach(envAdapter -> {
       if (envAdapter.enabled()) {