Implement an event handler

src/main/java/emu/grasscutter/server/event/Event.java

@@ -0,0 +1,33 @@
+package emu.grasscutter.server.event;
+
+import emu.grasscutter.Grasscutter;
+
+/**
+ * A generic server event.
+ */
+public abstract class Event {
+    private boolean cancelled = false;
+
+    /**
+     * Return the cancelled state of the event.
+     */
+    public boolean isCanceled() {
+        return this.cancelled;
+    }
+
+    /**
+     * Cancels the event if possible.
+     */
+    public void cancel() throws IllegalAccessException {
+        if(!(this instanceof Cancellable))
+            throw new IllegalAccessException("Event is not cancellable.");
+        this.cancelled = true;
+    }
+
+    /**
+     * Pushes this event to all listeners.
+     */
+    public void call() {
+        Grasscutter.getPluginManager().invokeEvent(this);
+    }
+}