[Java] Question on how to refer to two specific objects in a method

Question

So basically, we create four lines. One is created by giving a point (x,y) and the slope, the second is created by giving two points (x1, y1) and (x2,y2), the third is created as an equation in slope intercept form y=mx+b, and the fourth is given as an equation x=a with the line being vertical. To do that, we create four constructors.

Then, we're supposed to implement methods to see if the lines intersect, equal each other, or are parallel. My problem is, I have no clue how to code up "Take slope of line one and compare it to line three" "Take slope of line 2 and compare it to line 1" in the methods. If anyone could provide some insight I'd greatly appreciate it. My code right now is terribly convoluted, I know.

Links to Pastebin:

pastebin.com/zGrZL0D7

pastebin.com/A1K18gAH

Answer 1

Convert each line into a canonical form (e.g., the "two distinct points" form) and write a comparison function that operates on two lines presented in this form.

Answer 2

Your Line class does not need a set of variables for each line - just one set of doubles. Each Line object should only know its own variables.

Internally, your Line should be represented in general form (Ax + By + C = 0), and you should calculate A, B and C from the given representation. You may also want to store the slope as a fourth variable to make comparison easier. (your Line class should have private doubles - A, B, C and possibly m)

Your LineTester class is already set up to properly compare Line objects, if you finish writing the Line class. Inside the comparison methods you will use statements such as

if (m == other.m)

to implement your comparison logic.