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