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;
    }
}