Bouncing Balls

Ball

class Ball {
  
  float r;
  float vx;
  float vy;
  float xpos;
  float ypos;
  float m;
  int clrMode;
  int clr;
  int red;
  int green;
  int blue;
  
  boolean gravity;
  float g;
  
  Ball(float r, float xpos, float ypos){
    this.xpos = xpos;
    this.ypos = ypos;
    this.r = r;
    vx = 0;
    vy = 0;   
    m = 5;
    clr = 255;
    red = 0;
    green = 0;
    blue = 0;
    clrMode = 0;
    
    gravity = false;
    g = 0;
  }
  
  void display(){
    ellipse(xpos, ypos, 2*r, 2*r);
  }
  
  void update(){
    if(xpos >= width - r || xpos <= r){
      vx = -vx;
    }
    if(ypos >= height - r || ypos <= r){
      vy = -vy - g;
    }
    if(gravity){
      float tmp = vy;
      vy += g;
      if(tmp * vy < 0){
        vy = 0;
      }
    } 
    xpos += vx;
    if(xpos > width - r){
      xpos = width - r;
    } else if (xpos < r){
      xpos = r;
    }
    ypos += vy;
    if(ypos > height - r){
      ypos = height - r;
    } else if (ypos < r){
      ypos = r;
    } 
    getColor();
  } 
 
  void setColor(int clr){
    this.clr = clr;
    this.clrMode = 0;
  }
  
  void setColor(int red, int green, int blue){
    this.red = red;
    this.green = green;
    this.blue = blue;
    this.clrMode = 1;
  }
  
  void getColor(){
    if(this.clrMode == 0){
      fill(clr);
    } else {
      fill(red, green, blue);
    }
  }
  
  float getVelX(){
    return vx;
  }
  
  float getVelY(){
    return vy;
  }
  
  float getPosX(){
    return xpos;
  }
  
  float getPosY(){
    return ypos;
  }
  
  void setPosX(float p){
    this.xpos = p;
  }
  
  void setPosY(float p){
    this.xpos = p;
  }
  
  float getRadius(){
    return r;
  }
  
  void setGravity(boolean c){
    gravity = c;
  }
  
  void setGravity(boolean c, float g){
    gravity = c;
    this.g = g;
  }
  
  void setSpeed(float vx, float vy){
    this.vx = vx;
    this.vy = vy;
  }
  
  void setMass(float m){
    this.m = m;
  }
  
  float getMass(){
    return m;
  }
  
}

Balls

Ball[] balls;
int n;
float k;
float g;

void setup(){
  size(720, 720);
  background(125); 
  //noStroke();
  n = 5;
  k = 1;
  g = 0.3;
  
  balls = new Ball[n];
  for(int i = 0; i < n; i++){
    balls[i] = new Ball(10 + random(40), random(width*3/4) + 50, random(height*3/4) + 50);
    balls[i].setGravity(true, g);
    balls[i].setSpeed(k*(random(10) - 5), k*(random(10) - 5));
    balls[i].setColor((int)random(255), (int)random(255), (int)random(255));
    //balls[i].setColor((int)random(255));  
    balls[i].setMass(balls[i].getRadius() / 5);
  }
}

void draw(){
  background(125); 
  for(Ball ball : balls){
    if(n > 1){
      checkCrash(ball);
    }
    ball.update();
    ball.display();
  }
}
  
void checkCrash(Ball a){
  for(Ball b : balls){
    if(b != a){
       if(sqrt(sq(a.getPosX() - b.getPosX()) + sq(a.getPosY() - b.getPosY())) <= a.getRadius() + b.getRadius()){
           calculateCrash(a, b);
       }
    }
  }
}

void calculateCrash(Ball a, Ball b){
  float vxa, vya, vxb, vyb, vxa1, vya1, vxb1, vyb1;
  
  vxa = (a.getMass() - b.getMass()) / (a.getMass() + b.getMass()) * a.getVelX();
  vxa1 = 2*b.getMass() / (a.getMass() + b.getMass()) * b.getVelX();
  vxa += vxa1;
  
  vxb = 2*b.getMass() / (a.getMass() + b.getMass()) * a.getVelX();
  vxb1 = (b.getMass() - a.getMass()) / (a.getMass() + b.getMass()) * b.getVelX();
  vxb += vxb1;
  
  vya = (a.getMass() - b.getMass()) / (a.getMass() + b.getMass()) * a.getVelY();
  vya1 = 2*b.getMass() / (a.getMass() + b.getMass()) * b.getVelY();
  vya += vya1;
  
  vyb = 2*b.getMass() / (a.getMass() + b.getMass()) * a.getVelY();
  vyb1 = (b.getMass() - a.getMass()) / (a.getMass() + b.getMass()) * b.getVelY();
  vyb += vyb1;
  
  a.setSpeed(vxa, vya);
  b.setSpeed(vxb, vyb);
}