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 com.google.common.annotations.GwtCompatible; 20 import com.google.common.annotations.GwtIncompatible; 21 import com.google.common.collect.testing.Helpers; 22 23 import java.lang.reflect.Method; 24 25 /** 26 * Tests {@link java.util.List#hashCode}. 27 * 28 * @author George van den Driessche 29 */ 30 @GwtCompatible(emulated = true) 31 public class ListHashCodeTester<E> extends AbstractListTester<E> { testHashCode()32 public void testHashCode() { 33 int expectedHashCode = 1; 34 for (E element : getOrderedElements()) { 35 expectedHashCode = 31 * expectedHashCode + 36 ((element == null) ? 0 : element.hashCode()); 37 } 38 assertEquals( 39 "A List's hashCode() should be computed from those of its elements.", 40 expectedHashCode, getList().hashCode()); 41 } 42 43 /** 44 * Returns the {@link Method} instance for {@link #testHashCode()} so that 45 * list tests on unhashable objects can suppress it with 46 * {@code FeatureSpecificTestSuiteBuilder.suppressing()}. 47 */ 48 @GwtIncompatible("reflection") getHashCodeMethod()49 public static Method getHashCodeMethod() { 50 return Helpers.getMethod(ListHashCodeTester.class, "testHashCode"); 51 } 52 } 53