Sorting an array of objects based on one attribute only in Processing - processing

Question

I have a series of randomly plotted lines from a class called Line.
I have put all the objects into an array. I would like to connect any lines that are near each other with a dotted line. The simplest way I can think of doing this is to say if the x1 co-ordinate is <5 pixels from the x1 of another line, then draw a dotted line connecting the two x1 co-ordinates.
The problem I have is how to compare all the x1 co-ordinates with all the other x1 co-ordinates. I think this should involve 1. Sorting the array and then 2. Comparing consecutive array elements. However I want to sort only on x1 and I dont know how to do this.
Here is my code so far:
class Line{
public float x1;
public float y1;
public float x2;
public float y2;
public color cB;
public float rot;
public float fat;
public Line(float x1, float y1, float x2, float y2, color tempcB, float rot, float fat){
this.x1 = x1;
this.y1 = y1;
this.x2 = x2;
this.y2 = y2;
this.cB = tempcB;
this.rot = rot;
this.fat = fat;
};void draw(){
line(x1, y1, x2, y2);
//float rot = random(360);
float fat = random(5);
strokeWeight(fat);
////stroke (red,green,blue,opacity)
stroke(fat*100, 0, 0);
rotate(rot);
}
}
//Create array of objects
ArrayList<Line> lines = new ArrayList<Line>();
void setup(){
background(204);
size(600, 600);
for(int i = 0; i < 200; i++){
float r = random(500);
float s = random(500);
lines.add(new Line(r,s,r+10,s+10,color(255,255,255),random(360),random(5)));
}
//Draw out all the lines from the array
for(Line line : lines){
line.draw();
//Print them all out
println(line.x1,line.y1,line.x2,line.y2,line.cB,line.rot,line.fat);
}
}
//Now create connections between the elements
//If the x1 of the line is <5 pixels from another line then create a dotted line between the x1 points.

Answer 1

Like the other answer said, you need to compare both end points for this to make any sense. You also don't have to sort anything.
You should be using the dist() function instead of trying to compare only the x coordinate. The dist() function takes 2 points and gives you their distance. You can use this to check whether two points are close to each other or not:
float x1 = 75;
float y1 = 100;
float x2 = 25;
float y2 = 125;
float distance = dist(x1, y1, x2, y2);
if(distance < 100){
println("close");
}
You can use this function in your Line class to loop through other Lines and check for close points, or find the closest points, whatever you want.
As always, I recommend you try something out and ask another question if you get stuck.

Answer 2

The problem lies in the fact that a Line is composed of two points, and despite being tied together (pun intended), you need to check the points of each Line independently. The only point you really don't need to check is other point in the same Line instance.
In this case, it might be in your best interest to have a Point class. Line would then use Point instances to define both ends rather than the raw float coordinates. In this way, you can have both a list of Lines as well as a list of Points.
In this way you can sort Points by x coordinate or y coordinate and grab all points within 5 pixels of your point (and that isn't the same instance or other point in Line instance of course).
Being able to split handling into Points and Lines is important in that you're using multiple views to handle the same data. As a general rule, you should rearrange said data whenever it becomes cumbersome to deal with in its current form. However if I may make a recommendation, the sorting is not strictly necessary. If you're checking a single point with all other points, you'd have to sort repeatedly according to the current point which is more work than simply making a pass in a list to deal with all other points that are close enough.