001/* 002 * Copyright (C) 2008 The Guava Authors 003 * 004 * Licensed under the Apache License, Version 2.0 (the "License"); 005 * you may not use this file except in compliance with the License. 006 * You may obtain a copy of the License at 007 * 008 * http://www.apache.org/licenses/LICENSE-2.0 009 * 010 * Unless required by applicable law or agreed to in writing, software 011 * distributed under the License is distributed on an "AS IS" BASIS, 012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 013 * See the License for the specific language governing permissions and 014 * limitations under the License. 015 */ 016 017package com.google.common.collect.testing.testers; 018 019import static com.google.common.collect.testing.features.MapFeature.ALLOWS_NULL_KEYS; 020import static com.google.common.collect.testing.features.MapFeature.ALLOWS_NULL_VALUES; 021 022import com.google.common.annotations.GwtCompatible; 023import com.google.common.collect.testing.AbstractMapTester; 024import com.google.common.collect.testing.features.CollectionSize; 025import com.google.common.collect.testing.features.MapFeature; 026import java.util.Collection; 027import java.util.Map.Entry; 028import org.junit.Ignore; 029 030/** 031 * Tests {@link java.util.Map#hashCode}. 032 * 033 * @author George van den Driessche 034 * @author Chris Povirk 035 */ 036@GwtCompatible 037@Ignore // Affects only Android test runner, which respects JUnit 4 annotations on JUnit 3 tests. 038public class MapHashCodeTester<K, V> extends AbstractMapTester<K, V> { 039 public void testHashCode() { 040 int expectedHashCode = 0; 041 for (Entry<K, V> entry : getSampleEntries()) { 042 expectedHashCode += hash(entry); 043 } 044 assertEquals( 045 "A Map's hashCode() should be the sum of those of its entries.", 046 expectedHashCode, 047 getMap().hashCode()); 048 } 049 050 @CollectionSize.Require(absent = CollectionSize.ZERO) 051 @MapFeature.Require(ALLOWS_NULL_KEYS) 052 public void testHashCode_containingNullKey() { 053 Entry<K, V> entryWithNull = entry(null, v3()); 054 runEntryWithNullTest(entryWithNull); 055 } 056 057 @CollectionSize.Require(absent = CollectionSize.ZERO) 058 @MapFeature.Require(ALLOWS_NULL_VALUES) 059 public void testHashCode_containingNullValue() { 060 Entry<K, V> entryWithNull = entry(k3(), null); 061 runEntryWithNullTest(entryWithNull); 062 } 063 064 private void runEntryWithNullTest(Entry<K, V> entryWithNull) { 065 Collection<Entry<K, V>> entries = getSampleEntries(getNumEntries() - 1); 066 067 entries.add(entryWithNull); 068 069 int expectedHashCode = 0; 070 for (Entry<K, V> entry : entries) { 071 expectedHashCode += hash(entry); 072 } 073 074 resetContainer(getSubjectGenerator().create(entries.toArray())); 075 assertEquals( 076 "A Map's hashCode() should be the sum of those of its entries (where " 077 + "a null element in an entry counts as having a hash of zero).", 078 expectedHashCode, 079 getMap().hashCode()); 080 } 081 082 private static int hash(Entry<?, ?> e) { 083 return (e.getKey() == null ? 0 : e.getKey().hashCode()) 084 ^ (e.getValue() == null ? 0 : e.getValue().hashCode()); 085 } 086}