1 /* 2 * Copyright (C) 2007 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.google.android.collect; 18 19 import android.compat.annotation.UnsupportedAppUsage; 20 import android.os.Build; 21 import android.util.ArraySet; 22 23 import java.util.Collections; 24 import java.util.EnumSet; 25 import java.util.HashSet; 26 import java.util.SortedSet; 27 import java.util.TreeSet; 28 29 /** 30 * Provides static methods for creating mutable {@code Set} instances easily and 31 * other static methods for working with Sets. 32 * 33 */ 34 @android.ravenwood.annotation.RavenwoodKeepWholeClass 35 public class Sets { 36 37 /** 38 * Creates an empty {@code HashSet} instance. 39 * 40 * <p><b>Note:</b> if {@code E} is an {@link Enum} type, use {@link 41 * EnumSet#noneOf} instead. 42 * 43 * <p><b>Note:</b> if you only need an <i>immutable</i> empty Set, 44 * use {@link Collections#emptySet} instead. 45 * 46 * @return a newly-created, initially-empty {@code HashSet} 47 */ 48 @UnsupportedAppUsage newHashSet()49 public static <K> HashSet<K> newHashSet() { 50 return new HashSet<K>(); 51 } 52 53 /** 54 * Creates a {@code HashSet} instance containing the given elements. 55 * 56 * <p><b>Note:</b> due to a bug in javac 1.5.0_06, we cannot support the 57 * following: 58 * 59 * <p>{@code Set<Base> set = Sets.newHashSet(sub1, sub2);} 60 * 61 * <p>where {@code sub1} and {@code sub2} are references to subtypes of {@code 62 * Base}, not of {@code Base} itself. To get around this, you must use: 63 * 64 * <p>{@code Set<Base> set = Sets.<Base>newHashSet(sub1, sub2);} 65 * 66 * @param elements the elements that the set should contain 67 * @return a newly-created {@code HashSet} containing those elements (minus 68 * duplicates) 69 */ 70 @UnsupportedAppUsage newHashSet(E... elements)71 public static <E> HashSet<E> newHashSet(E... elements) { 72 int capacity = elements.length * 4 / 3 + 1; 73 HashSet<E> set = new HashSet<E>(capacity); 74 Collections.addAll(set, elements); 75 return set; 76 } 77 78 /** 79 * Creates an empty {@code SortedSet} instance. 80 * 81 * @return a newly-created, initially-empty {@code SortedSet}. 82 */ 83 @UnsupportedAppUsage newSortedSet()84 public static <E> SortedSet<E> newSortedSet() { 85 return new TreeSet<E>(); 86 } 87 88 /** 89 * Creates a {@code SortedSet} instance containing the given elements. 90 * 91 * @param elements the elements that the set should contain 92 * @return a newly-created {@code SortedSet} containing those elements (minus 93 * duplicates) 94 */ newSortedSet(E... elements)95 public static <E> SortedSet<E> newSortedSet(E... elements) { 96 SortedSet<E> set = new TreeSet<E>(); 97 Collections.addAll(set, elements); 98 return set; 99 } 100 101 /** 102 * Creates a {@code ArraySet} instance. 103 */ 104 @UnsupportedAppUsage newArraySet()105 public static <E> ArraySet<E> newArraySet() { 106 return new ArraySet<E>(); 107 } 108 109 /** 110 * Creates a {@code ArraySet} instance containing the given elements. 111 */ 112 @UnsupportedAppUsage(maxTargetSdk = Build.VERSION_CODES.R, trackingBug = 170729553) newArraySet(E... elements)113 public static <E> ArraySet<E> newArraySet(E... elements) { 114 int capacity = elements.length * 4 / 3 + 1; 115 ArraySet<E> set = new ArraySet<E>(capacity); 116 Collections.addAll(set, elements); 117 return set; 118 } 119 } 120