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/*
 * -----------------------------------------------------------------------
 * Copyright © 2013-2014 Meno Hochschild, 
 * -----------------------------------------------------------------------
 * This file (ChronoOperator.java) is part of project Time4J.
 *
 * Time4J is free software: You can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as published
 * by the Free Software Foundation, either version 2.1 of the License, or
 * (at your option) any later version.
 *
 * Time4J 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 Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with Time4J. If not, see .
 * -----------------------------------------------------------------------
 */

package net.time4j.engine;


/**
 * Applies a functional calculation on chronological entities and
 * yields the result as changed copy. 
 *
 * Technical note: This interface is only suitable in an
 * Java-pre8-environment (that is Java 6 + 7) if the type T is constrained
 * to a final type. Otherwise the compiler will fail when compiling
 * expressions like {@code entity.with(operator)} due to limited support
 * of type inference. This constraint does not exist with Java 8 and later. 
 *
 * @param    generic type of entities this operator can be applied to
 * @author  Meno Hochschild
 */
/*[deutsch]
 * Wendet auf chronologische Objekte eine funktionale Berechnung an und
 * liefert das geänderte Objekt zurück. 
 *
 * Technische Notiz: Dieses Interface ist in einer Java-pre-8-Umgebung
 * (also Java 6 + 7) nur dann geeignet, wenn der Typ T auf einen finalen Typ
 * eingeschränkt wird. Sonst gibt es wegen der mangelnden Typinferenz bei
 * Ausdrücken wie {@code entity.with(operator)} einen Compiler-Fehler. Ab
 * Java 8 besteht diese Einschränkung nicht mehr. 
 *
 * @param    generic type of entities this operator can be applied to
 * @author  Meno Hochschild
 */
// TODO: Ab Java 8 aktiv => extends UnaryOperator
public interface ChronoOperator {

    //~ Methoden ----------------------------------------------------------

    /**
     * Adjusts given entity and yields a changed copy of argument. 
     *
     * Will be called by {@link ChronoEntity#with(ChronoOperator)}. 
     *
     * @param   entity      chronological entity to be adjusted
     * @return  adjusted copy of argument which itself remains unaffected
     * @throws  ChronoException if there is no element rule for adjusting
     * @throws  IllegalArgumentException if any invalid value is tried
     * @throws  ArithmeticException in case of numerical overflow
     */
    /*[deutsch]
     * Passt die angegebene Entität an und liefert eine geänderte
     * Kopie des Arguments. 
     *
     * Wird von {@link ChronoEntity#with(ChronoOperator)} aufgerufen. 
     *
     * @param   entity      chronological entity to be adjusted
     * @return  adjusted copy of argument which itself remains unaffected
     * @throws  ChronoException if there is no element rule for adjusting
     * @throws  IllegalArgumentException if any invalid value is tried
     * @throws  ArithmeticException in case of numerical overflow
     */
    T apply(T entity);

}