Hey guys.

I'm trying to make a sketch where some balls move, and there is connections drawing between them.
I feel like I succeed to do it, but It seems to me that each connection (lines) are displayed two times. One time with the good positionning, and a second time with the positionning of the previous frame or something like this.
Here I set a low framerate to show this.

I would greatly appreciate if someone could help me pointing out what is the problem.

1. final int objNB = 8;
2. final int circlesNB = 3;
3. int taillemax = 90;
4. int maxspeed = 5;
5. Circle[] circles = new Circle[objNB];
6. void setup()
7. {
8.   size(1024,576);
9.   background(0);
10.   smooth();
11.   frameRate(15);
12.   for(int i = 0;i<objNB;i++)
13.   {
14.     circles[i] = new Circle(random(taillemax-10,taillemax));
15.   }
16. }
17. class Circle
18. {
19.   float Xpos,Ypos;
20.   float Xspeed,Yspeed;
21.   float taille;
22.   float taille2;
23.   float taille3;
24.  
25.   Circle(float taillebase)
26.   {
27.     this(random(taillebase,width-taillebase),random(taillebase,height-taillebase),random(-maxspeed,maxspeed),random(-maxspeed,maxspeed),taillebase);
28.   }
29.   Circle(float x,float y, float sx, float sy, float r)
30.   {
31.     Xpos = x;
32.     Ypos = y;
33.     Xspeed = sx;
34.     Yspeed = sy;
35.     taille = r;
36.     taille2 = random(1,r);
37.     taille3 = random(1,r);
38.   }
39.  
40.   void drawlines()
41.   {
42.         for(int j=0; j<objNB; j++)
43.     {
44.      if (Xpos != circles[j].Xpos && Ypos != circles[j].Ypos){
45.      if (dist(Xpos,Ypos,circles[j].Xpos,circles[j].Ypos) < 350)
46.       {
47.        stroke(255,255,255);
48.        line(Xpos,Ypos,circles[j].Xpos,circles[j].Ypos);
49.       }
50.       }
51.     }
52.   }
53.   void move()
54.   {
55.     Xpos += Xspeed;
56.     if (Xpos < taille || Xpos > width - taille)
57.     {
58.       Xspeed = -Xspeed;
59.       Xpos += Xspeed;
60.     }
61.    
62.     Ypos += Yspeed;
63.     if (Ypos < taille || Ypos > height - taille)
64.     {
65.       Yspeed = -Yspeed;
66.       Ypos += Yspeed;
67.     }
68.   }
69.  
70.   void display()
71.   {
72.     noStroke();
73.     fill(255,255,255,20);
74.     ellipse(Xpos, Ypos, taille * 2, taille * 2);
75.     ellipse(Xpos, Ypos, taille2 * 2, taille2 * 2);
76.     ellipse(Xpos, Ypos, taille3 * 2, taille3 * 2);
77.   }
78. }
79.    
80. void draw()
81. {
82.   background(0);
83.   for(int i = 0;i<objNB;i++)
84.   {
85.     circles[i].drawlines();   
86.     circles[i].display();
87.     circles[i].move();
88.   }
89. }

Thank you in advance.