[fix]单例对象的工厂类

rpc-framework-common/src/main/java/github/javaguide/factory/SingletonFactory.java

@@ -11,30 +11,25 @@ import java.util.Map;
  * @createTime 2020年06月03日 15:04:00
  */
 public final class SingletonFactory {
-    private static volatile Map<String, Object> objectMap = new HashMap<>();
+    private static final Map<String, Object> OBJECT_MAP = new HashMap<>();
 
     private SingletonFactory() {
     }
 
     public static <T> T getInstance(Class<T> c) {
         String key = c.toString();
-        Object instance = objectMap.get(key);
-        if (instance == null) {
-            synchronized (SingletonFactory.class) {
-                instance = objectMap.get(key);
-                if (instance == null) {
-                    try {
-                        instance = c.getDeclaredConstructor().newInstance();
-                        objectMap.put(key, instance);
-                    } catch (IllegalAccessException | InstantiationException e) {
-                        throw new RuntimeException(e.getMessage(), e);
-                    } catch (NoSuchMethodException | InvocationTargetException e) {
-                        e.printStackTrace();
-                    }
+        Object instance;
+        synchronized (SingletonFactory.class) {
+            instance = OBJECT_MAP.get(key);
+            if (instance == null) {
+                try {
+                    instance = c.getDeclaredConstructor().newInstance();
+                    OBJECT_MAP.put(key, instance);
+                } catch (IllegalAccessException | InstantiationException | NoSuchMethodException | InvocationTargetException e) {
+                    throw new RuntimeException(e.getMessage(), e);
                 }
             }
         }
-
         return c.cast(instance);
     }
 }