ComparableComparator.java

/*
 * Copyright 2020 Gregory Graham.
 *
 * Commercial licenses are available, please contact info@gregs.co.nz for details.
 * 
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 * or send a letter to Creative Commons, PO Box 1866, Mountain View, CA 94042, USA.
 * 
 * You are free to:
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 *             You may not use the material for commercial purposes.
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package nz.co.gregs.dbvolution.utility.comparators;

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

/**
 *
 * @author gregorygraham
 * @param <T> The class for which this comparator works
 */
public class ComparableComparator<T extends Comparable<? super T>> implements Comparator<T>, Serializable {

	private static final long serialVersionUID = 1L;

	private static final Map<Class<?>, ComparableComparator<?>> map = new HashMap<>(0);

	public static <C extends Comparable<? super C>> ComparableComparator<C> forClass(Class<C> aClass) {
		@SuppressWarnings("unchecked")
		ComparableComparator<C> got = (ComparableComparator<C>) map.get(aClass);
		if (got == null) {
			got = new ComparableComparator<C>(aClass);
			map.put(aClass, got);
		}
		return got;
	}

	private ComparableComparator() {
		super();
	}

	private ComparableComparator(Class<T> aClass) {
		this();
	}

	@Override
	public int compare(T o1, T o2) {
		if (o1 != null) {
			return o1.compareTo(o2);
		} else {
			return o2 == null ? 0 : 1;
		}
	}

}