1/*
2 * Copyright (C) 2017 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
17package com.android.server.wm;
18
19import java.util.ArrayList;
20
21/**
22 * An {@link ArrayList} with extended functionality to be used as the children data structure in
23 * {@link WindowContainer}.
24 */
25class WindowList<E> extends ArrayList<E> {
26
27    void addFirst(E e) {
28        add(0, e);
29    }
30
31    E peekLast() {
32        return size() > 0 ? get(size() - 1) : null;
33    }
34
35    E peekFirst() {
36        return size() > 0 ? get(0) : null;
37    }
38}
39