Prefer List/Map/Set as declaring type over their implementations

Unless your are using a method declared in subclasses of an
interface, it is better to use the interface as declaring type.
One advantage of this is that changing used implementation will
be much simpler (you will have less declarations to edit).

app/src/main/java/com/topjohnwu/magisk/utils/CallbackHandler.java

@@ -2,13 +2,15 @@ package com.topjohnwu.magisk.utils;
 
 import java.util.HashMap;
 import java.util.HashSet;
+import java.util.Map;
+import java.util.Set;
 
 public class CallbackHandler {
 
-    private static HashMap<Event, HashSet<EventListener>> listeners = new HashMap<>();
+    private static Map<Event, Set<EventListener>> listeners = new HashMap<>();
 
     public static void register(Event event, EventListener listener) {
-        HashSet<EventListener> list = listeners.get(event);
+        Set<EventListener> list = listeners.get(event);
         if (list == null) {
             list = new HashSet<>();
             listeners.put(event, list);
@@ -17,21 +19,21 @@ public class CallbackHandler {
     }
 
     public static void unRegister(Event event) {
-        HashSet<EventListener> list = listeners.remove(event);
+        Set<EventListener> list = listeners.remove(event);
         if (list != null) {
             list.clear();
         }
     }
 
     public static void unRegister(Event event, EventListener listener) {
-        HashSet<EventListener> list = listeners.get(event);
+        Set<EventListener> list = listeners.get(event);
         if (list != null) {
             list.remove(listener);
         }
     }
 
     private static void triggerCallback(Event event) {
-        HashSet<EventListener> list = listeners.get(event);
+        Set<EventListener> list = listeners.get(event);
         if (list != null) {
             for (EventListener listener : list) {
                 listener.onTrigger(event);