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