org.threeten.bp.temporal.TemporalQuery.scala Maven / Gradle / Ivy

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/*
 * Copyright (c) 2007-present, 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:
 *
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 *    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
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package org.threeten.bp.temporal

/**
 * Strategy for querying a temporal object.
 *
 * 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.
 *
 * 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.
 *
 * 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)}:
 *  // these two lines are equivalent, but the second approach is recommended temporal =
 * thisQuery.queryFrom(temporal); temporal = temporal.query(thisQuery);  It is recommended to
 * use the second approach, {@code query(TemporalQuery)}, as it is a lot clearer to read in code.
 *
 * The most common implementations are method references, such as {@code LocalDate::from} and {@code
 * ZoneId::from}. Further implementations are on {@link TemporalQueries}. Queries may also be
 * defined by applications.
 *
 * Specification for implementors This interface places no restrictions on the mutability
 * of implementations, however immutability is strongly recommended.
 */
trait TemporalQuery[+R] {

  /**
   * Queries the specified temporal object.
   *
   * 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.
   *
   * 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)}:  // these
   * two lines are equivalent, but the second approach is recommended temporal =
   * thisQuery.queryFrom(temporal); temporal = temporal.query(thisQuery);  It is recommended
   * to use the second approach, {@code query(TemporalQuery)}, as it is a lot clearer to read in
   * code.
   *
   * Specification for implementors 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.
   *
   * 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}.
   *
   * 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
   */
  def queryFrom(temporal: TemporalAccessor): R
}