FloatCmp.java Source code

Introduction

Here is the source code for FloatCmp.java

Source

/**
 * Floating-point comparisons.
 * @author Ian F. Darwin, http://www.darwinsys.com/
 * @version $Id: FloatCmp.java,v 1.11 2004/02/09 03:33:56 ian Exp $
 */
public class FloatCmp {
    final static double EPSILON = 0.0000001;

    public static void main(String[] argv) {
        double da = 3 * .3333333333;
        double db = 0.99999992857;

        // Compare two numbers that are expected to be close.
        if (da == db) {
            System.out.println("Java considers " + da + "==" + db);
            // else compare with our own equals method
        } else if (equals(da, db, 0.0000001)) {
            System.out.println("True within epsilon " + EPSILON);
        } else {
            System.out.println(da + " != " + db);
        }

        // Show that comparing two NaNs is not a good idea:
        double d1 = Double.NaN;
        double d2 = Double.NaN;
        if (d1 == d2)
            System.err.println("Comparing two NaNs incorrectly returns true.");
        if (!new Double(d1).equals(new Double(d2)))
            System.err.println("Double(NaN).equal(NaN) incorrectly returns false.");
    }

    /** Compare two doubles within a given epsilon */
    public static boolean equals(double a, double b, double eps) {
        if (a == b)
            return true;
        // If the difference is less than epsilon, treat as equal.
        return Math.abs(a - b) < eps;
    }

    /** Compare two doubles, using default epsilon */
    public static boolean equals(double a, double b) {
        if (a == b)
            return true;
        // If the difference is less than epsilon, treat as equal.
        return Math.abs(a - b) < EPSILON * Math.max(Math.abs(a), Math.abs(b));
    }
}