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 package com.android.car.util; 17 18 import java.util.ArrayDeque; 19 import java.util.Iterator; 20 import java.util.function.Predicate; 21 import java.util.stream.Stream; 22 23 /** 24 * This class keeps track of a limited fixed number of sample data points, correctly removing 25 * older samples as new ones are added, and it allows inspecting the samples, as well as 26 * easily answering N out of M questions. 27 * 28 * @param <T> data to iterate 29 */ 30 public class SlidingWindow<T> implements Iterable<T> { 31 private final ArrayDeque<T> mElements; 32 private final int mMaxSize; 33 34 /** TODO: add javadoc */ SlidingWindow(int size)35 public SlidingWindow(int size) { 36 mMaxSize = size; 37 mElements = new ArrayDeque<>(mMaxSize); 38 } 39 40 /** TODO: add javadoc */ add(T sample)41 public void add(T sample) { 42 if (mElements.size() == mMaxSize) { 43 mElements.removeFirst(); 44 } 45 mElements.addLast(sample); 46 } 47 48 /** TODO: add javadoc */ addAll(Iterable<T> elements)49 public void addAll(Iterable<T> elements) { 50 elements.forEach(this::add); 51 } 52 53 @Override iterator()54 public Iterator<T> iterator() { 55 return mElements.iterator(); 56 } 57 58 /** TODO: add javadoc */ stream()59 public Stream<T> stream() { 60 return mElements.stream(); 61 } 62 63 /** TODO: add javadoc */ size()64 public int size() { 65 return mElements.size(); 66 } 67 68 /** TODO: add javadoc */ count(Predicate<T> predicate)69 public int count(Predicate<T> predicate) { 70 return (int) stream().filter(predicate).count(); 71 } 72 } 73