class bullet
{
  float x,y;
  float targetX,targetY;
  bullet(float _x, float _y, float _targetX, float _targetY)
  {
    x=_x;
    y=_y;
    targetX=_targetX;
    targetY=_targetY;
  }

  void move()
  {
    //change x and y by some ammount to get to target.
  }

  void draw()
  {
    ellipse(x,y,10,10);
  }
}

bullet[] bullets;

void setup()
{
  //normal setup stuff...
  bullets=new bullet[0];
}

void draw()
{
  for(int i=0;i<bullets.length;i++)
  {
    bullets[i].move();
    bullets[i].draw();
  }
}

void mousePressed
{
  bullets=(bullet[])append(new bullet(0,0,mouseX,mouseY),bullets);
}