I have an Arduino UNO.  I was able to write the program for Serial Mouse sketch shown on that page and it seemed to be ok and I was able to download it to the board.  However when I tried to create the processing sketch it doesn't want to complete. It says: Can not find a class or type named "Dimension"

here is the entire processing code:

// Processing Sketch

/*
 * ArduinoMouse.pde (Processing sketch)
 */
 
 /* WARNING: this sketch takes over your mouse
  * Press escape to close running sketch
  */
 
  import java.awt.AWTException;
  import java.awt.Robot;
  import processing.serial.*;
 
  Serial    myPort;  // Create object from Serial class
  arduMouse myMouse; // Craete arduino controlled mouse
 
  public static final short LF = 10;          // ASCII linefeed
  public static final short portIndex = 1;    // select the com port,
                                              // 0 is the first port
                                             
  int posX, posY, btn;  // data from msg fields will be stored here
 
  void setup() {
    size(200, 200);
    println(Serial.list());
    println(" Connecting to -> " + Serial.list()[portIndex]);
    myPort = new Serial(this,Serial.list()[portIndex], 9600);
    myMouse = new arduMouse();
    btn = 0; // turn mouse off until requested by Arduino message
  }
 
  void draw() {
    if ( btn != 0)
       myMouse.move(posX, posY);  // move mouse to recieve x and y position
  }
  void serialEvent(Serial p) {
    String message = myPort.readStringUntil(LF); // read serial data
    if ( message != null)
    {
      //print(message);
      String [] data = message.split(","); // Split teh comma-seperated meassage
      if ( data[0].equals("Data"))// check for data header
      {
       if( data.length > 3 )
     {
       try {
         posX = Integer.parseInt(data[1]);
         posY = Integer.parseInt(data[2]);
         btn  = Integer.parseInt(data[3]);
       }
       catch (Throwable t) {
         println("."); // parse error
         print(message);
       }
     }
    }
  }
 }
 
 class arduMouse {
   Robot myRobot;  // create object from Robot class;
   static final short rate = 4; // multiplier to adjust movement rate
   int centerX, centerY;
   arduMouse() {
     try {
       myRobot = new Robot();
     }
     catch (AWTException e) {
       e.printStackTrace();
     }
     Dimension screen = java.awt.Toolkit.getDefaultToolkit().getScreenSize();
     centerY = (int)screen.getHeight() / 2;
     centerX = (int)screen.getWidth() / 2;
   }
   // method to move mouse from center of screen by given offset
  void move(int offsetX, int offsetY) {
    myRobot.mouseMove(centerX + (rate* offsetX), centerY - (rate * offsetY));
  }
 }