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.testing.testers; 18 19 import static com.google.common.collect.testing.features.MapFeature.ALLOWS_NULL_KEYS; 20 import static com.google.common.collect.testing.features.MapFeature.ALLOWS_NULL_VALUES; 21 22 import com.google.common.annotations.GwtCompatible; 23 import com.google.common.collect.testing.AbstractMapTester; 24 import com.google.common.collect.testing.features.CollectionSize; 25 import com.google.common.collect.testing.features.MapFeature; 26 27 import java.util.Collection; 28 import java.util.Map; 29 30 /** 31 * Tests {@link java.util.Map#hashCode}. 32 * 33 * @author George van den Driessche 34 * @author Chris Povirk 35 */ 36 @GwtCompatible 37 public class MapHashCodeTester<K, V> extends AbstractMapTester<K, V> { 38 public void testHashCode() { 39 int expectedHashCode = 0; 40 for (Map.Entry<K, V> entry : getSampleEntries()) { 41 expectedHashCode += hash(entry); 42 } 43 assertEquals( 44 "A Map's hashCode() should be the sum of those of its entries.", 45 expectedHashCode, getMap().hashCode()); 46 } 47 48 @CollectionSize.Require(absent = CollectionSize.ZERO) 49 @MapFeature.Require(ALLOWS_NULL_KEYS) 50 public void testHashCode_containingNullKey() { 51 Map.Entry<K, V> entryWithNull = entry(null, samples.e3.getValue()); 52 runEntryWithNullTest(entryWithNull); 53 } 54 55 @CollectionSize.Require(absent = CollectionSize.ZERO) 56 @MapFeature.Require(ALLOWS_NULL_VALUES) 57 public void testHashCode_containingNullValue() { 58 Map.Entry<K, V> entryWithNull = entry(samples.e3.getKey(), null); 59 runEntryWithNullTest(entryWithNull); 60 } 61 62 private void runEntryWithNullTest(Map.Entry<K, V> entryWithNull) { 63 Collection<Map.Entry<K, V>> entries = getSampleEntries(getNumEntries() - 1); 64 65 entries.add(entryWithNull); 66 67 int expectedHashCode = 0; 68 for (Map.Entry<K, V> entry : entries) { 69 expectedHashCode += hash(entry); 70 } 71 72 resetContainer(getSubjectGenerator().create(entries.toArray())); 73 assertEquals( 74 "A Map's hashCode() should be the sum of those of its entries (where " 75 + "a null element in an entry counts as having a hash of zero).", 76 expectedHashCode, getMap().hashCode()); 77 } 78 79 private static int hash(Map.Entry<?, ?> e) { 80 return (e.getKey() == null ? 0 : e.getKey().hashCode()) 81 ^ (e.getValue() == null ? 0 : e.getValue().hashCode()); 82 } 83 } 84
