Important Notice:

Practice-It will be discontinued as of November 1st, 2024. After this date, the website will remain online for a transitional period, but login will be restricted to University of Washington NetID authentication. This marks the next phase towards the platform's full retirement. Thank you for your use and support of the application over the years.

If you are looking for an alternative, a similar tool, CodeStepByStep, was developed independently by the original author of Practice-It, and is available at codestepbystep.com**

logo Practice-It logo

Main Page → Problems → Solve a Problem

BJP4 Exercise 8.17: isCollinearLine

Author: Marty Stepp (on 2016/09/08)

Add the following method to your Line class: 

public boolean isCollinear(Point p)

Returns true if the given point is collinear with the points of this line; that is, if, when this Line is stretched infinitely, it would eventually hit the given point. Points are collinear if a straight line can be drawn that connects them. Two basic examples are three points that have the same x- or y-coordinate. The more general case can be determined by calculating the slope of the line between each pair of points and checking whether this slope is the same for all pairs of points. Use the formula (y2 - y1) / (x2 - x1) to determine the slope between two points (x1, y1) and (x2, y2).

(Note that this formula fails for points with identical x-coordinates, so this will have to be a special case in your code.) Since Java's double type is imprecise, round all slope values to four digits past the decimal point before you compare them.

(You don't need to write the class header or declare the fields; assume that this is already done for you. Just write your constructor's complete code in the box provided.) See the previous exercises for a description of the Line class and its public members.

Type your solution here:


This is a partial class problem. Submit code that will become part of an existing Java class as described. You do not need to write the complete class, just the portion described in the problem.

You must log in before you can solve this problem.


Log In

If you do not understand how to solve a problem or why your solution doesn't work, please contact your TA or instructor.
If something seems wrong with the site (errors, slow performance, incorrect problems/tests, etc.), please

Is there a problem? Contact a site administrator.