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