Hi all,
   This is my first post and I'm relatively new to programming.  I'm trying to write a program that will serve as a GUI for some projects that I want to do with my arduino.  I started by writing a program that uses a graphical slider like on a mixing board to change a value.  Right now, everything seems to set up right but when I click on my slider to change the value, it won't go any higher than 5%.  Any help or advice would be much appreciated.  Here is the code for my project:

slider vol; //slider that will theoretically modulate parameters sent to a
            //digital potentiometer controlling volume on a guitar effects pedal
PFont f;

void setup(){
  f= loadFont("AgencyFB-Reg-12.vlw");
  textFont(f, 20); 
  size(500, 500);
  vol= new slider("Volume", color(255,0,0),40, 40);
  frameRate(30);
}

void draw(){
  background(153);
 
 
  if(mousePressed && vol.B.overRect(vol.B.buttonX, vol.B.buttonY, vol.buttonW, vol.buttonH)) {
    vol.setBval(mouseY);
  }
  vol.display();
}

class slider{
  String label;
  color c;
  float slotX;
  float slotY;
 
  float slotH= 100;
  float slotW= 10;

  float buttonW= 30;
  float buttonH= 10;
  float buttonVal;
  button B;
 

   
  slider(String name, color slideC, int slideX, int slideY){
    label= name;
    c= slideC;
    slotX= slideX;
    slotY= slideY;
    B= this.new button();
    buttonVal= 0;
       
  }
 
  void display(){
    //slider label
    fill(c);
    textAlign(CENTER);
    text(label, slotX + (slotW / 2), slotY - 10);
   
    //slider slot position   
    stroke(255);
    fill(100);
    rect(slotX, slotY, slotW, slotH);
   
    B.show();
    textAlign(CENTER);
    //displays buttonVal at the bottom of the slider
    text(buttonVal + "%", slotX + slotW/2, slotY + slotH + 30);
  }
 
  //sets buttonVal to a value 0..100
  void setBval(float val){
    buttonVal= (slotY + slotH) - constrain(val, vol.slotY ,vol.slotY + vol.slotH);
  }
 
  //gets button value as a decimal percentage that can be used to determine button position
  float conBval(){
    float bPerc= buttonVal / 100;
    return bPerc;
  }
 
 
      /**inner class button of class slider, tracks button position and value*/ 
      class button{
       
        float buttonX= slotX + (slotW / 2) - (buttonW / 2);
        float buttonY= slotY + slotH - (buttonH / 2);
       
        button(){
        println("slot x = " + slotX + ", slotY is " + slotY);
        println("buttonX = " + buttonX + ", buttonY = " + buttonY);
        }
       
        //displays button at necessary location
        void show(){
          float Y= (slotY + slotH) - conBval()*slotH - buttonH/2;
          println("buttonVal= " + buttonVal + ", conBval() = " + conBval() + ", button Y pos = " + Y);
          //setBval(Y);
          stroke(c);
          fill(c);
          rect(buttonX, Y, buttonW, buttonH);
         

        }
       
        //determines whether mouse is over button
        boolean overRect(float x, float y, float W, float H){
          if (mouseX >= x && mouseX <= x + W &&
              mouseY >= y && mouseY <= y + H){
                return true;
              } else {
                return false;
              }
        }
}
}