1 /* 2 * Copyright (C) 2021 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 package com.android.systemui.util 18 19 import java.util.concurrent.CopyOnWriteArrayList 20 21 /** 22 * A collection of listeners, observers, callbacks, etc. 23 * 24 * This container is optimized for infrequent mutation and frequent iteration, with thread safety 25 * and reentrant-safety guarantees as well. Specifically, to ensure that 26 * [ConcurrentModificationException] is never thrown, this iterator will not reflect changes made to 27 * the set after the iterator is constructed. 28 */ 29 class ListenerSet<E : Any> 30 /** Private constructor takes the internal list so that we can use auto-delegation */ 31 private constructor(private val listeners: CopyOnWriteArrayList<E>) : 32 Collection<E> by listeners, IListenerSet<E> { 33 34 /** Create a new instance */ 35 constructor() : this(CopyOnWriteArrayList()) 36 addIfAbsentnull37 override fun addIfAbsent(element: E): Boolean = listeners.addIfAbsent(element) 38 39 override fun remove(element: E): Boolean = listeners.remove(element) 40 } 41