tec.uom.lib.common.util.NumberComparator Maven / Gradle / Ivy

Go to download
Show more of this group Show more artifacts with this name
Show all versions of uom-lib-common Show documentation
The newest version!
/*
 *  Units of Measurement Common Library for Java
 *  Copyright (c) 2005-2016, Jean-Marie Dautelle, Werner Keil, V2COM.
 *
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without modification,
 * are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice,
 *    this list of conditions and the following disclaimer.
 *
 * 2. 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.
 *
 * 3. Neither the name of JSR-363, Unit-API 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 "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
 * EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
package tec.uom.lib.common.util;

import static java.lang.Character.isDigit;
import static java.lang.Character.isSpaceChar;

import java.util.Comparator;

/**
 * Compares two {@linkplain Number} objects with each other
 * @author Werner
 * @version 0.1
 * @since 1.0.2
 */
public class NumberComparator implements Comparator {

	private NumberComparator() {
		// Singleton
	}

	protected static char charAt(String s, int i) {
		if (i >= s.length()) {
			return '\000';
		}

		return s.charAt(i);
	}

	protected int compareRight(String a, String b) {
		int bias = 0;
		int ia = 0;
		int ib = 0;
		while (true) {
			char ca = charAt(a, ia);
			char cb = charAt(b, ib);

			if ((!isDigit(ca)) && (!isDigit(cb))) {
				return bias;
			}
			if (!isDigit(ca)) {
				return -1;
			}
			if (!isDigit(cb)) {
				return 1;
			}
			if (ca < cb) {
				if (bias == 0) {
					bias = -1;
				}
			} else if (ca > cb) {
				if (bias == 0)
					bias = 1;
			} else if ((ca == 0) && (cb == 0))
				return bias;
			ia++;
			ib++;
		}
	}

	public int compare(Number o1, Number o2) {
		String a = o1.toString();
		String b = o2.toString();

		int ia = 0;
		int ib = 0;
		int nza;
		int nzb;
		while (true) {
			nza = nzb = 0;

			char ca = charAt(a, ia);
			char cb = charAt(b, ib);

			while ((isSpaceChar(ca)) || (ca == '0')) {
				if (ca == '0') {
					nza++;
				} else {
					nza = 0;
				}

				ca = charAt(a, ++ia);
			}

			while ((isSpaceChar(cb)) || (cb == '0')) {
				if (cb == '0') {
					nzb++;
				} else {
					nzb = 0;
				}

				cb = charAt(b, ++ib);
			}
			int result;
			if ((isDigit(ca)) && (isDigit(cb)) && ((result = compareRight(a.substring(ia), b.substring(ib))) != 0)) {
				return result;
			}

			if ((ca == 0) && (cb == 0)) {
				return nza - nzb;
			}

			if (ca < cb) {
				return -1;
			}
			if (ca > cb) {
				return 1;
			}

			ia++;
			ib++;
		}
	}

	private static NumberComparator INSTANCE;

	public static NumberComparator getInstance() {
		if (INSTANCE == null) {
			INSTANCE = new NumberComparator();
		}
		return INSTANCE;
	}
}