Java tutorial
/* * Copyright (c) 2012, 2013, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation. Oracle designates this * particular file as subject to the "Classpath" exception as provided * by Oracle in the LICENSE file that accompanied this code. * * This code is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. */ /* * This file is available under and governed by the GNU General Public * License version 2 only, as published by the Free Software Foundation. * However, the following notice accompanied the original version of this * file: * * Copyright (c) 2012, Stephen Colebourne & Michael Nascimento Santos * * All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions are met: * * * Redistributions of source code must retain the above copyright notice, * this list of conditions and the following disclaimer. * * * Redistributions in binary form must reproduce the above copyright notice, * this list of conditions and the following disclaimer in the documentation * and/or other materials provided with the distribution. * * * Neither the name of JSR-310 nor the names of its contributors * may be used to endorse or promote products derived from this software * without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */ package java.time.temporal; import java.time.DateTimeException; /** * Strategy for querying a temporal object. * <p> * Queries are a key tool for extracting information from temporal objects. * They exist to externalize the process of querying, permitting different * approaches, as per the strategy design pattern. * Examples might be a query that checks if the date is the day before February 29th * in a leap year, or calculates the number of days to your next birthday. * <p> * The {@link TemporalField} interface provides another mechanism for querying * temporal objects. That interface is limited to returning a {@code long}. * By contrast, queries can return any type. * <p> * There are two equivalent ways of using a {@code TemporalQuery}. * The first is to invoke the method on this interface directly. * The second is to use {@link TemporalAccessor#query(TemporalQuery)}: * <pre> * // these two lines are equivalent, but the second approach is recommended * temporal = thisQuery.queryFrom(temporal); * temporal = temporal.query(thisQuery); * </pre> * It is recommended to use the second approach, {@code query(TemporalQuery)}, * as it is a lot clearer to read in code. * <p> * The most common implementations are method references, such as * {@code LocalDate::from} and {@code ZoneId::from}. * Additional common queries are provided as static methods in {@link TemporalQueries}. * * @implSpec * This interface places no restrictions on the mutability of implementations, * however immutability is strongly recommended. * * @param <R> the type returned from the query * * @since 1.8 */ @FunctionalInterface public interface TemporalQuery<R> { /** * Queries the specified temporal object. * <p> * This queries the specified temporal object to return an object using the logic * encapsulated in the implementing class. * Examples might be a query that checks if the date is the day before February 29th * in a leap year, or calculates the number of days to your next birthday. * <p> * There are two equivalent ways of using this method. * The first is to invoke this method directly. * The second is to use {@link TemporalAccessor#query(TemporalQuery)}: * <pre> * // these two lines are equivalent, but the second approach is recommended * temporal = thisQuery.queryFrom(temporal); * temporal = temporal.query(thisQuery); * </pre> * It is recommended to use the second approach, {@code query(TemporalQuery)}, * as it is a lot clearer to read in code. * * @implSpec * The implementation must take the input object and query it. * The implementation defines the logic of the query and is responsible for * documenting that logic. * It may use any method on {@code TemporalAccessor} to determine the result. * The input object must not be altered. * <p> * The input temporal object may be in a calendar system other than ISO. * Implementations may choose to document compatibility with other calendar systems, * or reject non-ISO temporal objects by {@link TemporalQueries#chronology() querying the chronology}. * <p> * This method may be called from multiple threads in parallel. * It must be thread-safe when invoked. * * @param temporal the temporal object to query, not null * @return the queried value, may return null to indicate not found * @throws DateTimeException if unable to query * @throws ArithmeticException if numeric overflow occurs */ R queryFrom(TemporalAccessor temporal); }