1/* 2 * Copyright (c) 2012, 2013, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. Oracle designates this 8 * particular file as subject to the "Classpath" exception as provided 9 * by Oracle in the LICENSE file that accompanied this code. 10 * 11 * This code is distributed in the hope that it will be useful, but WITHOUT 12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 14 * version 2 for more details (a copy is included in the LICENSE file that 15 * accompanied this code). 16 * 17 * You should have received a copy of the GNU General Public License version 18 * 2 along with this work; if not, write to the Free Software Foundation, 19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 20 * 21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 22 * or visit www.oracle.com if you need additional information or have any 23 * questions. 24 */ 25 26/* 27 * This file is available under and governed by the GNU General Public 28 * License version 2 only, as published by the Free Software Foundation. 29 * However, the following notice accompanied the original version of this 30 * file: 31 * 32 * Copyright (c) 2012, Stephen Colebourne & Michael Nascimento Santos 33 * 34 * All rights reserved. 35 * 36 * Redistribution and use in source and binary forms, with or without 37 * modification, are permitted provided that the following conditions are met: 38 * 39 * * Redistributions of source code must retain the above copyright notice, 40 * this list of conditions and the following disclaimer. 41 * 42 * * Redistributions in binary form must reproduce the above copyright notice, 43 * this list of conditions and the following disclaimer in the documentation 44 * and/or other materials provided with the distribution. 45 * 46 * * Neither the name of JSR-310 nor the names of its contributors 47 * may be used to endorse or promote products derived from this software 48 * without specific prior written permission. 49 * 50 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 51 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 52 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR 53 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR 54 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, 55 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, 56 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR 57 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF 58 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING 59 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS 60 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 61 */ 62package java.time.temporal; 63 64import java.time.DateTimeException; 65 66/** 67 * Strategy for querying a temporal object. 68 * <p> 69 * Queries are a key tool for extracting information from temporal objects. 70 * They exist to externalize the process of querying, permitting different 71 * approaches, as per the strategy design pattern. 72 * Examples might be a query that checks if the date is the day before February 29th 73 * in a leap year, or calculates the number of days to your next birthday. 74 * <p> 75 * The {@link TemporalField} interface provides another mechanism for querying 76 * temporal objects. That interface is limited to returning a {@code long}. 77 * By contrast, queries can return any type. 78 * <p> 79 * There are two equivalent ways of using a {@code TemporalQuery}. 80 * The first is to invoke the method on this interface directly. 81 * The second is to use {@link TemporalAccessor#query(TemporalQuery)}: 82 * <pre> 83 * // these two lines are equivalent, but the second approach is recommended 84 * temporal = thisQuery.queryFrom(temporal); 85 * temporal = temporal.query(thisQuery); 86 * </pre> 87 * It is recommended to use the second approach, {@code query(TemporalQuery)}, 88 * as it is a lot clearer to read in code. 89 * <p> 90 * The most common implementations are method references, such as 91 * {@code LocalDate::from} and {@code ZoneId::from}. 92 * Additional common queries are provided as static methods in {@link TemporalQueries}. 93 * 94 * @implSpec 95 * This interface places no restrictions on the mutability of implementations, 96 * however immutability is strongly recommended. 97 * 98 * @param <R> the type returned from the query 99 * 100 * @since 1.8 101 */ 102@FunctionalInterface 103public interface TemporalQuery<R> { 104 105 /** 106 * Queries the specified temporal object. 107 * <p> 108 * This queries the specified temporal object to return an object using the logic 109 * encapsulated in the implementing class. 110 * Examples might be a query that checks if the date is the day before February 29th 111 * in a leap year, or calculates the number of days to your next birthday. 112 * <p> 113 * There are two equivalent ways of using this method. 114 * The first is to invoke this method directly. 115 * The second is to use {@link TemporalAccessor#query(TemporalQuery)}: 116 * <pre> 117 * // these two lines are equivalent, but the second approach is recommended 118 * temporal = thisQuery.queryFrom(temporal); 119 * temporal = temporal.query(thisQuery); 120 * </pre> 121 * It is recommended to use the second approach, {@code query(TemporalQuery)}, 122 * as it is a lot clearer to read in code. 123 * 124 * @implSpec 125 * The implementation must take the input object and query it. 126 * The implementation defines the logic of the query and is responsible for 127 * documenting that logic. 128 * It may use any method on {@code TemporalAccessor} to determine the result. 129 * The input object must not be altered. 130 * <p> 131 * The input temporal object may be in a calendar system other than ISO. 132 * Implementations may choose to document compatibility with other calendar systems, 133 * or reject non-ISO temporal objects by {@link TemporalQueries#chronology() querying the chronology}. 134 * <p> 135 * This method may be called from multiple threads in parallel. 136 * It must be thread-safe when invoked. 137 * 138 * @param temporal the temporal object to query, not null 139 * @return the queried value, may return null to indicate not found 140 * @throws DateTimeException if unable to query 141 * @throws ArithmeticException if numeric overflow occurs 142 */ 143 R queryFrom(TemporalAccessor temporal); 144 145} 146