chore[field]: field visibility

event/src/main/java/com/zfoo/event/manager/EventBus.java

@@ -45,7 +45,7 @@ public abstract class EventBus {
      * EN: The size of the thread pool. Event's thread pool is often used to do time-consuming operations, so set it a little bigger
      * CN: 线程池的大小. event的线程池经常用来做一些耗时的操作，所以要设置大一点
      */
-    public static final int EXECUTORS_SIZE = Runtime.getRuntime().availableProcessors() * 2;
+    private static final int EXECUTORS_SIZE = Runtime.getRuntime().availableProcessors() * 2;
 
     private static final ExecutorService[] executors = new ExecutorService[EXECUTORS_SIZE];