Attempts to determine equality between any subclasses of number. - Java java.lang

Java examples for java.lang:double Format

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Description

Attempts to determine equality between any subclasses of number.

Demo Code

/*//from w  w  w  .  j  a  v  a  2  s  .  c  o m
 * Java-Math is a math library written for Java 1.6+ that is primarily 
 * intended to help with 2D and 3D graphics, physics, and other related
 * mathematical operations. 
 *  
 * Copyright (C) 2014  Alec Sobeck and Matthew Robertson
 *
 * Java-Math is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version. 
 *
 * This program 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 */
import java.math.BigDecimal;

public class Main{
    /**
     * Attempts to determine equality between any subclasses of number. This method is special because it attempts to account 
     * for rounding errors in doubles and floats. Doubles are checked for equality with a call to 
     * {@link #approximatelyEqual(double, double, int)} to 13 places and floats are checked for equality with a call to
     * {@link #approximatelyEqual(float, float)}. 
     * <br> <br>
     * If the data types are not both doubles or floats then they will be compared for equality based on the rules of
     * a.equals(b). In general this will mean that variables with the same type and value are equal, but variables with 
     * the same value but a different type will not be equal. IE 444L == 444L, but 444L != 444.
     * @param a a Number to compare for equality
     * @param b a Number to compare for equality
     * @return a boolean, true if the values are of the same type and value, but otherwise false
     */
    public static boolean equal(Number a, Number b) {
        if (a instanceof Double && b instanceof Double) {
            return DecimalHelper.approximatelyEqual((Double) a, (Double) b,
                    13);
        } else if (a instanceof Float && b instanceof Float) {
            return DecimalHelper.approximatelyEqual((Float) a, (Float) b);
        } else {
            return a.equals(b);
        }
    }
    /**
     * Checks if two doubles are approximately equal. This is done by seeing if the doubles are within 
     * 1E-6 of each other. 
     * @param a the first double to check for approximate equality
     * @param b the second double to check for approximate equality
     * @return a boolean, true, if the numbers are reasonably close together; otherwise false
     */
    public static boolean approximatelyEqual(double a, double b) {
        return (Math.abs(a - b) < 1e-6) ? true : false;
    }
    /**
     * Checks if two doubles are approximately equal. This is done by seeing if the doubles are within 
     * 1 * 10^-(allowedDecimals) of each other. 
     * @param a the first double to check for approximate equality
     * @param b the second double to check for approximate equality
     * @param allowedDecimals the number of decimal places allowed before comparing the two values. If this goes beyond
     * a certain value it may be impossible to compare equality as doubles can hold only a certain number of decimals.
     * @return a boolean, true, if the numbers are within the specified tolerance of each other; otherwise false
     */
    public static boolean approximatelyEqual(double a, double b,
            int allowedDecimals) {
        return (Math.abs(a - b) < Math.pow(10, -1 * allowedDecimals)) ? true
                : false;
    }
    /**
     * Checks if two floats are approximately equal. This is done by seeing if the floats are within 
     * 1E-6 of each other. 
     * @param a the first floats to check for approximate equality
     * @param b the second floats to check for approximate equality
     * @return a boolean, true, if the floats are reasonably close together; otherwise false
     */
    public static boolean approximatelyEqual(float a, float b) {
        return (Math.abs(a - b) < 1e-6) ? true : false;
    }
    /**
     * Checks if two floats are approximately equal. This is done by seeing if the floats are within 
     * 1 * 10^-(allowedDecimals) of each other. 
     * @param a the first floats to check for approximate equality
     * @param b the second floats to check for approximate equality
     * @param allowedDecimals the number of decimal places allowed before comparing the two values. If this goes beyond
     * a certain value it may be impossible to compare equality as floats can hold only a certain number of decimals.
     * @return a boolean, true, if the numbers are within the specified tolerance of each other; otherwise false
     */
    public static boolean approximatelyEqual(float a, float b,
            int allowedDecimals) {
        return (Math.abs(a - b) < Math.pow(10, -1 * allowedDecimals)) ? true
                : false;
    }
}

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