Modify a text file: $/balls.java

$/balls.java

//// Demo of Ball objects [BAM:2A18f] ////
// Several ball objects, moving around on the screen.
// Object-oriented programming (without arrays).

Ball one, two, three;
Ball four, five, six, seven, eight;
float helpX=10, helpY=10, helpLine=0;

void setup() { 
  size(800, 600); 
  smooth();
  begin();
}
void begin() {
  //// Create objects.  Initialize, as necessary.
  one=  new Ball( color(255, 0, 0), 1, "1" );
  two=  new Ball( color(0, 255, 0), 2, "2" );
  three=  new Ball( color(0, 0, 255), 3, "3" );
  four=  new Ball( color(255, 255, 0), 4, "4" );
  five=  new Ball( color(0, 255, 255), 5, "5" );
  six=  new Ball( color(255, 0, 255), 6, "6" );
  seven=  new Ball( color(255, 127, 0), 7, "8" );
  eight=  new Ball( color(0, 0, 0), 8, "8" );
  eight.fillNum=  color(255);
}

void draw() {
  //// Draw the next frame.
  background( 200, 200, 255 );
  if (key == '?') help();
  moveAll();
  collisions();
  showAll();
}

void moveAll() {
  //// Move all three balls.
  one.move();
  two.move();
  three.move();
  // More:
  four.move();    
  five.move();  
  six.move();  
  seven.move();    
  eight.move();
}

void collisions() {
  //// Check for collisions; exchange momentum.
  one.bounce( two );
  one.bounce( three );
  two.bounce( three );
  ////
  one.bounce(four);  
  one.bounce(five);  
  one.bounce(six);  
  one.bounce(seven);  
  one.bounce(eight);
  two.bounce(four);  
  two.bounce(five);  
  two.bounce(six);  
  two.bounce(seven);  
  two.bounce(eight);
  three.bounce(four);  
  one.bounce(five);  
  three.bounce(six);  
  three.bounce(seven);  
  three.bounce(eight);
  four.bounce(five);  
  four.bounce(six);  
  four.bounce(seven);  
  four.bounce(eight);
  five.bounce(six);  
  five.bounce(seven);  
  five.bounce(eight);
  six.bounce(seven);  
  six.bounce(eight);
  seven.bounce(eight);
}

void showAll() {
  //// Show all three balls.
  one.show();
  two.show();
  three.show();
  //// More
  four.show();  
  five.show();  
  six.show();  
  seven.show();  
  eight.show();
}

//// EVENT HANDLERS ////
void keyPressed() {
  //// Respond to different keys, when pressed.
  switch (key) {
  case '0':  
    begin();  
    break;
  case '1':  
    one.speedup();  
    break;
  case '2':  
    two.speedup();  
    break;
  case '3':  
    three.speedup();  
    break;
  case '4':  
    four.speedup();  
    break;
  case '5':  
    five.speedup();  
    break;
  case '6':  
    six.speedup();  
    break;
  case '7':  
    seven.speedup();  
    break;
  case '8':  
    eight.speedup();  
    break;

case 's':  
    frameRate( 2 );  
    break;
  case 'S':  
    frameRate( 30 );  
    break;
  }
}
void help() {
  //// Explain keys, etc.
  helpX=  width * 2 / 3;
  helpY=  100;
  next( "Click any ball to stop it." );
  next( "Number key (1,2,3) speeds up that ball" );
  next( "0 key restarts (with balls at random poisitions)" );
}
void next(String s ) {
  //// Show help text on next line.
  text( s, helpX, helpY );
  helpY += 12;      // Move down 12 pixels, for next line.
}
void mousePressed() {
  //// Click on ball to stop it.
  one.stop( mouseX, mouseY );
  two.stop( mouseX, mouseY );
  three.stop( mouseX, mouseY );
}

////  CLASS DEFINITIONS ////

// A "ball"  that moves, bounces, draws itself, etc.
class Ball
{
  float x=0, y=0, dx=3, dy=2;    // Coordiantes, velocity
  float radius=30;
  color c=  color(255);
  color fillNum=  color(0);
  int num=0;
  String s="0";
  //// CONSTRUCTOR(S) ////
  Ball( color c, int num, String s )
  {
    //// Construtor to set color, number, and name.  Random x,y & speed
    this.c=  c;
    this.num=  num;
    this.s=  s;
    //
    float r=  radius;
    x=  random( r, width-r );
    y=  random( r, height-r );
    dx=  random( 5 );
    dy= random( 3 );
  }

//// METHODS ////
  public void move() {        //// Move ball from x,y by dx,dy
    // First, check for bounce
    if (x<2*radius || x>width-2*radius) { 
      dx = -dx; 
      x += 2*dx;
    }
    if (y<2*radius || y>height-2*radius) { 
      dy = -dy; 
      y += 2*dy;
    }
    // Move
    x += dx;
    y += dy;
  }
  public void speedup() {        //// Increase speed of this ball.
    dx += 1;
    dy += 1;
  }
  public void stop(float x, float y) {        
    //// Stop if (x,y) is near this ball.
    if ( dist(x, y, this.x, this.y ) < radius ) {
      dx=0;
      dy=0;
    }
  }
  public void bounce( Ball other ) {        
    //// Bounce if other (x,y) is near this ball.
    if ( dist( other.x, other.y, this.x, this.y ) < radius ) {
      float t;
      t=other.dx; 
      other.dx=this.dx; 
      this.dx=t;
      t=other.dy; 
      other.dy=this.dy; 
      this.dy=t;
      // Bounce away from each other.
      this.x += this.radius*this.dx;
      this.y += this.radius*this.dy;
      other.x += other.radius*other.dx;
      other.y += other.radius*other.dy;
    }
  }

public void show() {        //// Show the ball.
    fill(c);
    if (key == '=') whereami();
    ellipse( x, y, radius, radius );
    fill(fillNum);
    text( num, x-5, y+5 );    // Show # on ball
  }
  void whereami() {
    //// Display positions.
    float xx=  (int) 2*radius;  // Offsets for text
    float yy=  0;
    text( x, x+xx, y+12*yy++ );  
    text( y, x+xx, y+12*yy++ );
    text( c, x+xx, y+12*yy++ );    
    // Also show dx
    yy=0;
    xx=  (int) 2*radius;  // Offsets for text
    text( dx, x+xx+100, y+12*yy++ );  
    text( dy, x+xx+100, y+12*yy++ );
  }
}// END of class Ball //