C5X15a_Line.java

public class Line
{
        private double m;
        private double b;

        /**
                Constructor
                @param m is the slope of the line
                @param b is the y-intercept of the line
        */
        public Line(double m, double b)
        {
                this.m = m;
                this.b = b;
        }

        /**
                Constructor
                @param m is the slope of the line
                @param x1 is abcissa of a given point on the line
                @param y1 is ordinate of a given point on the line
        */
        public Line(double m, double x1, double y1)
        {
                //this.m = m;
                //this.b = -m*x1+y1;
                this(m, -m*x1+y1);
        }

        /**
                Constructor
                @param x1 is abcissa of a given point on the line
                @param y1 is ordinate of a given point on the line
                @param x2 is abcissa of another given point on the line
                @param y2 is ordinate of another given point on the line
        */
        public Line(double x1, double y1, double x2, double y2)
        {
                //this.m = (y2-y1)/(x2-x1);
                //this.b = -m*x1+y1;
                this((y2-y1)/(x2-x1),x1,y1);
        }

        /**
                Accessor
                @param other is another line to compare to this line
                @return true iff m1=m2
        */
        public boolean isParallel(Line other)
        {
                return m==other.getM();
        }

        /**
                Accessor
                @param other is another line to compare to this line
                @return true iff m1!=m2
        */
        public boolean intersects(Line other)
        {
                return !isParallel(other);
        }

        /**
                Accessor
                @param other is another line to compare to this line
                @return true iff m1=m2 and b1=b2
        */
        public boolean equals(Object other)
        {
                Line temp = (Line)other;
                return isParallel(temp) && b==temp.getB();
        }

        /**
                Accessor
                @return the slope of this line
        */
        private double getM()
        {
                return m;
        }

        /**
                Accessor
                @return the y-intercept of this line
        */
        private double getB()
        {
                return b;
        }

        /**
                Accessor
                @return the state of this line
        */
        public String toString()
        {
                return "y = " + m + "x + " + b;
        }

        /**
                Accessor
                @param other is another line to compare to this line
                @return the abcissa=(b2-b1)/(m1-m2) of the POI for this and other
        */
        public double getX(Line other)
        {
                return (other.getB()-b)/(m-other.getM());
        }

        /**
                Accessor
                @param other is another line to compare to this line
                @return the ordinate=m(b2-b1)/(m1-m2)+b of the POI for this and other
        */
        public double getY(Line other)
        {
                return m*getX(other)+b;
        }
}