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/**
 * The MIT License
 *
 * Copyright (C) 2015 Asterios Raptis
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy of this software and
 * associated documentation files (the "Software"), to deal in the Software without restriction,
 * including without limitation the rights to use, copy, modify, merge, publish, distribute,
 * sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all copies or
 * substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT
 * NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
 * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */
package de.alpharogroup.comparators;

import java.io.Serializable;
import java.util.Comparator;

/**
 * The class {@link NullCheckComparator} decorates another {@link Comparator} object to compare null
 * and non-null values. Before the decorated {@link Comparator} will be executed null check will be
 * executed. Over the flag 'nullIsGreaterThan' can be controlled whether null object values are
 * greater or less than non-null object values.
 *
 * @param 
 *            the generic type of the {@link Comparator} object that will be decorated
 */
public class NullCheckComparator implements Comparator, Serializable
{
	public static class NullCheckComparatorBuilder
	{

		private Comparator decoratedComparator;

		private boolean nullIsGreaterThan;

		NullCheckComparatorBuilder()
		{
		}

		public NullCheckComparator build()
		{
			return new NullCheckComparator(decoratedComparator, nullIsGreaterThan);
		}

		public NullCheckComparatorBuilder decoratedComparator(
			final Comparator decoratedComparator)
		{
			this.decoratedComparator = decoratedComparator;
			return this;
		}

		public NullCheckComparatorBuilder nullIsGreaterThan(final boolean nullIsGreaterThan)
		{
			this.nullIsGreaterThan = nullIsGreaterThan;
			return this;
		}

		@Override
		public String toString()
		{
			return "NullCheckComparator.NullCheckComparatorBuilder(decoratedComparator="
				+ this.decoratedComparator + ", nullIsGreaterThan=" + this.nullIsGreaterThan + ")";
		}
	}

	/**
	 * The Constant serialVersionUID.
	 */
	private static final long serialVersionUID = 1L;

	public static  NullCheckComparatorBuilder builder()
	{
		return new NullCheckComparatorBuilder();
	}

	/**
	 * Factory method to create a new {@link NullCheckComparator} object from the given
	 * {@link Comparator} object.
	 *
	 * @param 
	 *            the generic type of the {@link Comparator} object that will be decorated
	 * @param decoratedComparator
	 *            the {@link Comparator} object that will be decorated
	 * @return the new decorated {@link Comparator} object
	 */
	public static  Comparator of(final Comparator decoratedComparator)
	{
		return NullCheckComparator. builder().decoratedComparator(decoratedComparator).build();
	}

	/**
	 * Factory method to create a new {@link NullCheckComparator} object from the given
	 * {@link Comparator} object.
	 *
	 * @param 
	 *            the generic type of the {@link Comparator} object that will be decorated
	 * @param decoratedComparator
	 *            the {@link Comparator} object that will be decorated
	 * @param nullIsGreaterThan
	 *            the flag that specifies if null objects is greater than non null objects.
	 * @return the new {@link NullCheckComparator} object
	 */
	public static  NullCheckComparator of(final Comparator decoratedComparator,
		final boolean nullIsGreaterThan)
	{
		return NullCheckComparator. builder().decoratedComparator(decoratedComparator)
			.nullIsGreaterThan(nullIsGreaterThan).build();
	}

	/**
	 * The decorated comparator.
	 */
	private final Comparator decoratedComparator;

	/**
	 * The flag that specifies if null objects is greater than non null objects.
	 */
	private final boolean nullIsGreaterThan;

	/**
	 * Instantiates a {@link NullCheckComparator} from the given {@link Comparator} object. The flag
	 * nullIsGreaterThan is set to false so null objects are smaller then non null objects.
	 *
	 * @param decoratedComparator
	 *            the {@link Comparator} object that will be decorated
	 */
	public NullCheckComparator(final Comparator decoratedComparator)
	{
		this(decoratedComparator, false);
	}

	/**
	 * Instantiates a {@link NullCheckComparator} from the given {@link Comparator} object and the
	 * given flag.
	 *
	 * @param decoratedComparator
	 *            the {@link Comparator} object that will be decorated
	 * @param nullIsGreaterThan
	 *            the flag that specifies if null objects is greater than non null objects.
	 */
	public NullCheckComparator(final Comparator decoratedComparator,
		final boolean nullIsGreaterThan)
	{
		if (decoratedComparator == null)
		{
			throw new IllegalArgumentException("Given decoratedComparator may not be null.");
		}
		this.decoratedComparator = decoratedComparator;
		this.nullIsGreaterThan = nullIsGreaterThan;
	}

	/**
	 * {@inheritDoc}
	 */
	@Override
	public int compare(final T object, final T compareWithObject)
	{
		final Integer nullCheck = ComparatorExtensions.nullCheck(object, compareWithObject,
			this.nullIsGreaterThan);
		if (nullCheck != null)
		{
			return nullCheck.intValue();
		}
		return this.decoratedComparator.compare(object, compareWithObject);
	}
}