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Partly generated model of the fields that represent columns in the database. Fields can be used to produce special predicates and functions that contain metadata that Speedment can analyze runtime.

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/**
 *
 * Copyright (c) 2006-2017, Speedment, Inc. All Rights Reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); You may not
 * use this file except in compliance with the License. You may obtain a copy of
 * the License at:
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations under
 * the License.
 */
package com.speedment.runtime.field.comparator;

import com.speedment.runtime.field.Field;

import java.util.Comparator;

/**
 * A specialized {@link Comparator} that contains meta data information about 
 * the field that is being compared.
 * 
 * Implementations of this interface are immutable. Equality is based upon the
 * equality of the {@link #getField() field}-identifier, the 
 * {@link #getNullOrder() null strategy} and the {@link #isReversed() order}.
 * 
 * @param   the entity type
 * 
 * @author Emil Forslund
 * @since  3.0.2
 */
public interface FieldComparator
extends Comparator {

    /**
     * Returns the field that created this comparator.
     * 
     * @return  the field
     */
    Field getField();
    
    /**
     * Returns the strategy used when {@code null} values are encountered. If
     * the order {@link NullOrder#NONE} is specified, then no guarantees will be
     * made regarding the order of entities where the field value is 
     * {@code null}.
     * 
     * @return  the null order strategy
     */
    NullOrder getNullOrder();
    
    /**
     * Returns {@code true} if this comparator reverses the natural order of the
     * values in the current field. A reversed order descends from high values
     * to low.
     * 
     * @return  {@code true} if reversed (descending), else {@code false}
     */
    boolean isReversed();
    
    /**
     * Returns a new {@code FieldComparator} that order entities in the opposite
     * orders compared to this comparator. For an example, if this comparator
     * orders entities based on a column 'firstname' in descending order, then
     * the returned {@code FieldComparator} will be ordering entities based on
     * 'firstname' in ascending order.
     * 
     * @return  a new reverse comparator
     */
    @Override
    FieldComparator reversed();
}