VectorMathsUtil.java

package esiea.tools.vector3d;
/**
 * Utility class used when computing the hash code for vector maths
 * objects containing float or double values.
 */
class VectorMathsUtil {
     /**
     * Returns the representation of the specified floating-point
     * value according to the IEEE 754 floating-point "double format"
     * bit layout, after first mapping -0.0 to 0.0. This method is
     * identical to Double.doubleToLongBits(double) except that an
     * integer value of 0L is returned for a floating-point value of
     * -0.0. This is done for the purpose of computing a hash code
     * that satisfies the contract of hashCode() and equals(). The
     * equals() method in each class does a pair-wise "=="
     * test on each floating-point field in the class (e.g., x, y, and
     * z for a Tuple3d). Since 0.0 == -0.0 returns true, we
     * must also return the same hash code for two objects, one of
     * which has a field with a value of -0.0 and the other of which
     * has a corresponding field with a value of 0.0.
     *
     * @param d an input double precision floating-point number
     * @return the integer bits representing that floating-point
     * number, after first mapping -0.0f to 0.0f
     */
    static long doubleToLongBits(double d) {
        // Check for +0 or -0
        if (d == 0.0) {
            return 0L;
        }
        else {
            return Double.doubleToLongBits(d);
        }
    }


    /**
     * Do not construct an instance of this class.
     */
    private VectorMathsUtil() {
    }
}