1 /* 2 * Copyright (C) 2008 The Guava Authors 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.common.collect; 18 19 import com.google.common.annotations.GwtCompatible; 20 import com.google.common.base.Function; 21 import com.google.common.base.Predicate; 22 import com.google.common.collect.Maps.EntryTransformer; 23 24 import java.lang.reflect.Array; 25 import java.util.Collections; 26 import java.util.Map; 27 import java.util.NavigableMap; 28 import java.util.NavigableSet; 29 import java.util.Set; 30 import java.util.SortedMap; 31 import java.util.SortedSet; 32 33 /** 34 * Methods factored out so that they can be emulated differently in GWT. 35 * 36 * @author Hayward Chan 37 */ 38 @GwtCompatible(emulated = true) 39 final class Platform { 40 /** 41 * Returns a new array of the given length with the same type as a reference 42 * array. 43 * 44 * @param reference any array of the desired type 45 * @param length the length of the new array 46 */ newArray(T[] reference, int length)47 static <T> T[] newArray(T[] reference, int length) { 48 Class<?> type = reference.getClass().getComponentType(); 49 50 // the cast is safe because 51 // result.getClass() == reference.getClass().getComponentType() 52 @SuppressWarnings("unchecked") 53 T[] result = (T[]) Array.newInstance(type, length); 54 return result; 55 } 56 newSetFromMap(Map<E, Boolean> map)57 static <E> Set<E> newSetFromMap(Map<E, Boolean> map) { 58 return Collections.newSetFromMap(map); 59 } 60 61 /** 62 * Configures the given map maker to use weak keys, if possible; does nothing 63 * otherwise (i.e., in GWT). This is sometimes acceptable, when only 64 * server-side code could generate enough volume that reclamation becomes 65 * important. 66 */ tryWeakKeys(MapMaker mapMaker)67 static MapMaker tryWeakKeys(MapMaker mapMaker) { 68 return mapMaker.weakKeys(); 69 } 70 mapsTransformEntriesSortedMap( SortedMap<K, V1> fromMap, EntryTransformer<? super K, ? super V1, V2> transformer)71 static <K, V1, V2> SortedMap<K, V2> mapsTransformEntriesSortedMap( 72 SortedMap<K, V1> fromMap, 73 EntryTransformer<? super K, ? super V1, V2> transformer) { 74 return (fromMap instanceof NavigableMap) 75 ? Maps.transformEntries((NavigableMap<K, V1>) fromMap, transformer) 76 : Maps.transformEntriesIgnoreNavigable(fromMap, transformer); 77 } 78 mapsAsMapSortedSet(SortedSet<K> set, Function<? super K, V> function)79 static <K, V> SortedMap<K, V> mapsAsMapSortedSet(SortedSet<K> set, 80 Function<? super K, V> function) { 81 return (set instanceof NavigableSet) 82 ? Maps.asMap((NavigableSet<K>) set, function) 83 : Maps.asMapSortedIgnoreNavigable(set, function); 84 } 85 setsFilterSortedSet(SortedSet<E> set, Predicate<? super E> predicate)86 static <E> SortedSet<E> setsFilterSortedSet(SortedSet<E> set, 87 Predicate<? super E> predicate) { 88 return (set instanceof NavigableSet) 89 ? Sets.filter((NavigableSet<E>) set, predicate) 90 : Sets.filterSortedIgnoreNavigable(set, predicate); 91 } 92 mapsFilterSortedMap(SortedMap<K, V> map, Predicate<? super Map.Entry<K, V>> predicate)93 static <K, V> SortedMap<K, V> mapsFilterSortedMap(SortedMap<K, V> map, 94 Predicate<? super Map.Entry<K, V>> predicate) { 95 return (map instanceof NavigableMap) 96 ? Maps.filterEntries((NavigableMap<K, V>) map, predicate) 97 : Maps.filterSortedIgnoreNavigable(map, predicate); 98 } 99 Platform()100 private Platform() {} 101 } 102