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