Java error: <identifier> expected timer.start() ;

Question

How do I fix this error?

error: expected timer.start()

import java.awt.event.ActionEvent ;
import java.awt.event.ActionListener ;
import javax.swing.JFrame ;
import javax.swing.Timer ;
/**
   This class illustrates using a Timer with a listener
   The listener illustrates using an interface.
   The program also illustrates that the inner class has access
   to constants in the local environment, but not variables.

   This is an example from the book, so the answer is there.
   Your job is 
   1. write the line that makes the Rectangle component, 
      remembering that it will have to be a constant.
   2. write the listener so that every time the timer ticks, it 
      moves the rectangle in the component by (dx, dy) = (DELTA, DELTA).
 */
public class RectangleComponentViewerWithTimer
{
    private static final int FRAME_WIDTH = 300 ;
    private static final int FRAME_HEIGHT = 400 ;
    private static final int DELTA = 2 ;
    private static final int LIMIT = 30 ;
    private static final int INTERVAL = 400 ;

    public static void main(String[] args)
    {
        //-----------Start below here. To do: approximate lines of code = 12
        // 1. create the RectangleComponent1 object called component.  
        //Hint: component will be used in the inner class
        RectangleComponent1 component = new RectangleComponent1();
        //1. define class TimerListener, an ActionListener
        class TimerListener implements ActionListener
        {//
            //2. instance variable count starting at zero ; 
            int count = 0;
            //3. actionPerformed method signature ; 
            public void actionPerformed(ActionEvent event)
            {//
                //4. increment count ; 
                count++;
                //5. tell component to moveBoxBy DELTA and DELTA ; 
                component.moveBoxBy(DELTA, DELTA);
                //6. when count reaches the LIMIT 
                if (count == LIMIT)
                    //7. print component.toString() ; 
                    System.out.println(component.toString());
                    //8. stop the application
                    System.exit(0);
                }//
            }//
        }//
        //9. make the listener
        ActionListener listener = new TimerListener();
        //10. make the timer based on INTERVAL and listener
        Timer timer = new Timer(INTERVAL, listener);
        //11. start the timer
        timer.start() ;
        //-----------------End here. Please do not remove this comment. Reminder: no changes outside the todo regions.
        JFrame frame = new JFrame() ;
        frame.add(component) ;
        frame.setSize(FRAME_WIDTH, FRAME_HEIGHT) ;
        frame.setTitle("Animated rectangle.") ;
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE) ;
        frame.setVisible(true) ;
    }
}

RectangleComponentViewerWithTimer.java:58: error: <identifier> expected
    timer.start() ;
               ^
RectangleComponentViewerWithTimer.java:61: error: <identifier> expected
    frame.add(component) ;
             ^
RectangleComponentViewerWithTimer.java:61: error: <identifier> expected
    frame.add(component) ;
                       ^
RectangleComponentViewerWithTimer.java:62: error: <identifier> expected
    frame.setSize(FRAME_WIDTH, FRAME_HEIGHT) ;
                 ^
RectangleComponentViewerWithTimer.java:62: error: <identifier> expected
    frame.setSize(FRAME_WIDTH, FRAME_HEIGHT) ;
                             ^
RectangleComponentViewerWithTimer.java:62: error: <identifier> expected
    frame.setSize(FRAME_WIDTH, FRAME_HEIGHT) ;
                                           ^
RectangleComponentViewerWithTimer.java:63: error: <identifier> expected
    frame.setTitle("Animated rectangle.") ;
                  ^
RectangleComponentViewerWithTimer.java:63: error: illegal start of type
    frame.setTitle("Animated rectangle.") ;
                   ^
RectangleComponentViewerWithTimer.java:64: error: <identifier> expected
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE) ;
                                  ^
RectangleComponentViewerWithTimer.java:64: error: <identifier> expected
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE) ;
                                                       ^
RectangleComponentViewerWithTimer.java:65: error: <identifier> expected
    frame.setVisible(true) ;

Answer 1

You look to be messing yourself with poor code formatting. Match your curly braces and you'll see that you have some code outside of a method.

Your formatting is causing you to think you have a curly brace where you don't:

            if (count == LIMIT)  // ***** no curly brace here *****
                //7. print component.toString() ; 
                System.out.println(component.toString());
                //8. stop the application
                System.exit(0);
            }   // **** this does not belong to the if block!

Because of this, all code from ActionListener listener = new TimerListener(); on down is sitting naked in the class, outside of any method or constructor.

Key point: code formatting isn't about pretty code, it's about debuggable code.

Other recs:

• If you can use an IDE such as NetBeans, Eclipse or Intellij, consider doing so. While these guys have a learning curve, it is eventually worth it, since they compile your code on the fly and tell you immediately if you have a compilation error.
• Regardless, you should check for compilation errors frequently.
• And when you find one, you should not add any new code to your program until all compilation problems are fixed. Else you may end up with a rat's nest of problems, where you end up fixing one problem, and then 5 more pop up.