I assume that you mean this tutorial if not please put a link in.

Anyway I copied the code from the tutorial and it ran fine for me. I have copied the code below.

1. Car myCar1;
2. Car myCar2; // Two objects!
3. 
   
4. void setup() {
5.   size(200,200);
6.   // Parameters go inside the parentheses when the object is constructed.
7.   myCar1 = new Car(color(255,0,0),0,100,2);
8.   myCar2 = new Car(color(0,0,255),0,10,1);
9. }
10. 
    
11. void draw() {
12.   background(255);
13.   myCar1.drive();
14.   myCar1.display();
15.   myCar2.drive();
16.   myCar2.display();
17. }
18. 
    
19. // Even though there are multiple objects, we still only need one class.
20. // No matter how many cookies we make, only one cookie cutter is needed.
21. class Car {
22.   color c;
23.   float xpos;
24.   float ypos;
25.   float xspeed;
26.   // The Constructor is defined with arguments.
27.   Car(color tempC, float tempXpos, float tempYpos, float tempXspeed) {
28.     c = tempC;
29.     xpos = tempXpos;
30.     ypos = tempYpos;
31.     xspeed = tempXspeed;
32.   }
33. 
    
34.   void display() {
35.     stroke(0);
36.     fill(c);
37.     rectMode(CENTER);
38.     rect(xpos,ypos,20,10);
39.   }
40. 
    
41.   void drive() {
42.     xpos = xpos + xspeed;
43.     if (xpos > width) {
44.       xpos = 0;
45.     }
46.   }
47. }

Thanks for your answer !
I needed to remove processing (2.0b7 W64) and I reloaded it and your code worked.
Now when I tried with my first OOP program the debugger says unexpected token : int
and the line 17 is highlighted.
I don't understand. Could you help me Please ? Thanks a lot.

1. SerialGraph sg;
2. void setup() {
3.   size(600,600);
4.   SerialGraph sg = new SerialGraph(255,500,500,400,400);
5. }
6. void draw(){
7.   background(240);
8.   sg.trace();
9. }
10. Class SerialGraph(){
11.   int drawArrayColor;
12.   int xDrawArraySize;
13.   int yDrawArraySize;
14.   int xWindowSize;
15.   int yWindowSize;
16. // Constructor
17. SerialGraph (int dac, int xws, int yws, int xdas, int ydas) {
18.   drawArrayColor = dac;
19.   xWindowSize = xdws;
20.   yWindowSize = ydws;
21.   xDrawArraySize = xdas;
22.   yDrawArraySize = ydas;
23. }
24. void trace(){
25.   rectmode(CORNER);
26.   fill(drawArrayColor);
27.   rect(xWindowSize-60,yWindowSize-50,xDrawArraySize,yDrawArraySize);
28.   }
29. }

hmmm....

line 10 "class" needs to be written with a small letter c

there are actually more errors,

• no () allowed in line 10
• xdws line 19 & ydws in line 20
• line 4 not say SerialGraph again, because that makes it a local var!!! You defined it already in
  line 1.

Greetings, Chrisir   

1. SerialGraph sg;
2. void setup() {
3.   size(600, 600);
4.   sg = new SerialGraph(255, 500, 500, 400, 400);
5. }
6. void draw() {
7.   background(240);
8.   sg.trace();
9. }
10. class SerialGraph {
11.   int drawArrayColor;
12.   int xDrawArraySize;
13.   int yDrawArraySize;
14.   int xWindowSize;
15.   int yWindowSize;
16.   // Constructor
17.   SerialGraph (int dac, int xws, int yws, int xdas, int ydas) {
18.     drawArrayColor = dac;
19.     xWindowSize = xws;
20.     yWindowSize = yws;
21.     xDrawArraySize = xdas;
22.     yDrawArraySize = ydas;
23.   }
24.   void trace() {
25.     //  rectmode(CORNER);
26.     fill(drawArrayColor);
27.     rect(xWindowSize-60, yWindowSize-50, xDrawArraySize, yDrawArraySize);
28.   }
29. }

 

Thanks for your help !
but after I modified the sketck I have ever an issue : the debugger says : "the constructor SerialGraph(int,int,int,int,int) is undefinedand the line 4 is highlighted. I don't find the solution.

1. SerialGraph sg;
2. 
   
3. void setup() {
4.   size(600,600);
5.   sg = new SerialGraph(200,50,50,25,25);
6. }
7. 
   
8. void draw(){
9.   background(200);
10.   sg.trace();
11. }
12. 
    
13. class SerialGraph {
14.   int drawArrayColor;
15.   int xDrawArraySize;
16.   int yDrawArraySize;
17.   int xWindowSize;
18.   int yWindowSize;
19. // Constructor
20. SerialGraph(int dac, int xws, int yws, int xdas, int ydas){
21.   drawArrayColor = dac;
22.   xWindowSize = xws;
23.   yWindowSize = yws;
24.   xDrawArraySize = xdas;
25.   yDrawArraySize = ydas;
26. }
27. 
    
28. void trace(){
29.   rectmode(CORNER);
30.   fill(drawArrayColor);
31.   rect(xWindowSize,yWindowSize,xDrawArraySize,yDrawArraySize);
32.   }
33. }

I have to comment this line out:

1.   rectmode(CORNER);

otherwise it works on my computer. Weird.


your error can either occur when you misspell something or when the number (or types) of parameters do not match between the constructor and your line 4. You need 5 times an int in both places, constructor and your line 4.

Sorry, I can't spot an error.

rectmode should be rectMode

The code worked for me - I didn't get an undefined constructor error and BTW line 4 is the size() method call.