I hope this will make some sense, but I am wondering about this, and I can't understand how Processing works, maybe someone will be able to clarify this for me.

So, for example, in the following code, I increase the fade value until it reaches a specific limit.

1. int fade = 0;

   
   

   void setup(){

     size (400,400); 

   }

   
   

   void draw(){

     fade++;

     fade = constrain(fade, 0, 255);

     println (fade);

   }

   
   

How can I stop the program from constantly updating this value? So, if I print the value I will be receiving per every frame the same value, however I want to make sure that this stop. 

Giving another example, if I use the controlP5 slider, you may notice that the value of the slider is printed only when the value changes, and not constantly. Therefore I would like to be able to control in the same manner the value in the first example.

2. import controlP5.*;
3. 
   
4. ControlP5 cp5;
5. int newValue;
6. 
   
7. void setup() {
8.   size(640, 250);
9.   noStroke();
10.   frameRate(30);
11. 
    
12.   cp5 = new ControlP5(this);
13.   cp5.addSlider("slider").setPosition(20, 100).setSize(150, 20).setRange(0, 255).setValue(255);
14. }
15. 
    
16. void draw() {
17.   background(80);
18. }
19. 
    
20. void slider (int theSlider) {
21.   newValue = theSlider;
22.   println(newValue);
23. }