Create a counter that increments once a second until a given number of seconds is reached

[Luke Stamper]

I am trying to get user input to start a counter and end a counter. Right now, the error I am getting is...

F:\Object Java\Assignments\Assignment 7\TimerJavaRanch.java:58: error: int cannot be dereferenced
number.setValue(number);
^

Also, I have not inserted a loop to to restart the program (I didn't want to loop anything until I got the program working).


Here is the Example Output for how my program should run:

--------------------Configuration: <Default>--------------------
This progam tests a timer.
Enter a start number of seconds
5
Enter an end number of seconds
11

CounterController Starting.

6...
7...
8...
9...
10...
11...

Continue?(y/n)
y
Enter a start number of seconds
0
Enter an end number of seconds
4

CounterController Starting.

1...
2...
3...
4...

Continue?(y/n)
n

Process completed.

import java.util.Scanner;

public class Timer extends Thread
{
    private NumberDisplay number;
    public static final int ONE_SECONDS = 1000;
    public  static boolean finished = true;
    private int endSec;
    private int startSec;
    private String displayString;

    public int Timer(int secArg)
    {
        this.startSec = secArg;
        number = new NumberDisplay(startSec);
       // number = new setTimer(startSec);
        updateDisplay();
    }

    public void timeTick()
    {
            number.increment();
        if(number.getValue() == 0) {
            number.increment();
        }
        updateDisplay();
    }

    public void run(){}

    public void countdown()
    {
        if(number.getDisplayValue().equals(endSec)){
            finished = false;
            System.out.println("Timer is completed.");
        }else {

            number.increment();
        if(number.getValue() == 0) {
            number.increment();

        }
        }
        updateDisplay();
    }

    public void setTimer(int number)
    {

        number.setValue(number);
        updateDisplay();
    }

    public String getTime()
    {
        return displayString;
    }

    private void updateDisplay()
    {
        displayString = number.getDisplayValue();
    }

    public static void main(String args[]){

    int startSec = 0;
    int endSec = 0;

		Scanner keyboard = new Scanner(System.in);

    	System.out.println("This program will test a timer.");
    	System.out.println("Enter a start number of seconds.");
    	startSec = keyboard.nextInt();
    	System.out.println("Enter an end number of seconds.");
    	endSec = keyboard.nextInt();


        Timer timer = new Timer(startSec);
        timer.start();
        while(finished){
            System.out.println("Time Is : " + timer.getTime());
            timer.countdown();
            try {
                Thread.sleep(ONE_SECONDS);
            }
            catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }
}


public class Number
{
    private int endSec;
    private int value;

    public Number(int rollOverLimit)
    {
        this.endSec = rollOverLimit;
        value = 0;
    }

    public int getendSec(){
    	return endSec;
    }

    public int getValue()
    {
        return value;
    }

    public String getDisplayValue()
    {
        if(value < 10) {
            return "0" + value;
        }
        else {
            return "" + value;
        }

    }

    public void setValue(int replacementValue)
    {
        if((replacementValue >= 0) && (replacementValue < endSec)) {
            value = replacementValue;
        }
    }

    public void increment()
    {
        value = (value + 1) % endSec;
    }
}

[Harsha Smith]

change line 50 to this as the method argument is shadowing the ObjectReference number

  this.number.setValue(number); 

[Luke Stamper]

Currently, my code compiles, but my counter is not working. The user input is basically ignored. The counter starts at zero and gets to 1, then it keeps repeating 1.

My goal is to start the counter at the first user input and end the counter at the second user input. Can anyone lend a helping hand and help me get my code straightened out?

Here is the example output....

--------------------Configuration: <Default>--------------------
This program will test a timer.
Enter a start number of seconds.
2
Enter an end number of seconds.
9
Time Is : 00
Time Is : 01
Time Is : 01
Time Is : 01

Process interrupted by user.

import java.util.Scanner;

public class Timer extends Thread
{
    private NumberDisplay number;
    public static final int ONE_SECONDS = 1000;
    public  static boolean finished = true;
    private int endSec;
    private int startSec;
    private String displayString;

    public Timer(int startSec, int endSec)
    {
        this.startSec = startSec;
        this.endSec = endSec;
        number = new NumberDisplay(startSec, endSec);
        updateDisplay();
    }

    public Timer()
    {
        this.setTimer(startSec);
        updateDisplay();
    }

    public void timeTick()
    {
            number.increment();
        if(number.getValue() == 0) {
            number.increment();
        }
        updateDisplay();
    }

    public void run(){}
    /**
     * Start countdown
     */
    public void counter()
    {
        if(number.getDisplayValue().equals(endSec)){
            finished = false;
            System.out.println("Timer is completed.");
        }else {

            number.increment();
        if(number.getValue() == 0) {
            number.increment();

        }
        }
        updateDisplay();
    }

    public void setTimer(int number)
    {

        this.number.setValue(number);
        updateDisplay();
    }

    public String getTime()
    {
        return displayString;
    }

    private void updateDisplay()
    {
        displayString = number.getDisplayValue();
    }

    public static void main(String args[]){

    int startSec = 0;
    int endSec = 0;

		Scanner keyboard = new Scanner(System.in);

    	System.out.println("This program will test a timer.");
    	System.out.println("Enter a start number of seconds.");
    	startSec = keyboard.nextInt();
    	System.out.println("Enter an end number of seconds.");
    	endSec = keyboard.nextInt();


        Timer timer = new Timer(startSec, endSec);
        timer.start();
        while(finished){
            System.out.println("Time Is : " + timer.getTime());
            timer.counter();
            try {
                Thread.sleep(ONE_SECONDS);
            }
            catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }
}


public class NumberDisplay
{
    private int endSec;
    private int startSec;
    private int startValue;
    private int limit;


    public NumberDisplay(int limit, int startValue)
    {
        this.endSec = limit;
        this.startSec = startValue;
    }



    /**
     * Return the current value.
     */
    public int getValue()
    {
        return startValue;
    }

    public String getDisplayValue()
    {
        if(startValue < 10) {
            return "0" + startValue;
        }
        else {
            return "" + startValue;
        }

    }

    public void setValue(int replacementValue)
    {
        if((replacementValue >= 0) && (replacementValue < endSec)) {
            startValue = replacementValue;
        }
    }

    public void increment()
    {
        startValue = (startValue + 1) % endSec;
    }

    public void decrement()
    {
        if(startValue>0)
            startValue = (startValue - 1) % endSec;

    }
}

[Rob Spoor]

You pass values 2 and 9 to the NumberDisplay constructor. However, that constructor uses the 2 as the limit (end) and 9 as the start. Swap the parameters around in the constructor.

After that your program will go to 8, then go back to 1. The reason is simple - startValue will never be the same as endSec, because if it would the mod (% endSec) turns it into 0 again.

[Luke Stamper]

I swapped the parameters around and my counter still starts at zero and goes to infinity. There must be a problem somewhere else in the code i'm not seeing?

To stop the counter, I am trying to figure out a way to have the counter number = endSec. Logically, I think that makes sense to stop the program.

[Luke Stamper]

So i've switched my code around....here is what i'm trying to do

In this program, there will be 3 classes. Your test program will input a start and end number of seconds. Call the CounterController only from your test program. The controller will create an instance of CounterModel with the initial value and call increment until the end value is reached. The CounterModel will wait 1 second, increment its counter and then display its counter by calling CounterView. Use Thread.sleep(1000); to delay 1 second.

I am having a lot of trouble with my methods in various classes.

I'm currently getting these errors:

--------------------Configuration: <Default>--------------------
F:\Object Java\Assignments\Assignment 7\CounterController\src\CounterController.java:16: error: cannot find symbol
Display();
^
symbol: method Display()
location: class CounterController
F:\Object Java\Assignments\Assignment 7\CounterController\src\CounterController.java:21: error: cannot find symbol
counterValue.setCounterValue(startValue);
^
symbol: method setCounterValue(int)
location: variable counterValue of type CounterView
F:\Object Java\Assignments\Assignment 7\CounterController\src\CounterController.java:22: error: cannot find symbol
Display();
^
symbol: method Display()
location: class CounterController
F:\Object Java\Assignments\Assignment 7\CounterController\src\CounterController.java:44: error: cannot find symbol
System.out.println("Time Is : " + counter.getTime());
^
symbol: method getTime()
location: variable counter of type CounterController
F:\Object Java\Assignments\Assignment 7\CounterController\src\CounterController.java:45: error: cannot find symbol
counter.counterMode();
^
symbol: method counterMode()
location: variable counter of type CounterController
5 errors

Process completed.

--------------------Configuration: <Default>--------------------
F:\Object Java\Assignments\Assignment 7\CounterController\src\CounterModel.java:23: error: cannot find symbol
Display();
^
symbol: method Display()
location: class CounterModel
F:\Object Java\Assignments\Assignment 7\CounterController\src\CounterModel.java:29: error: cannot find symbol
Display();
^
symbol: method Display()
location: class CounterModel
F:\Object Java\Assignments\Assignment 7\CounterController\src\CounterModel.java:38: error: cannot find symbol
Display();
^
symbol: method Display()
location: class CounterModel
3 errors

Process completed.

import java.util.Scanner;

public class CounterController extends Thread{

private int startValue;
private int endValue;
public static final	int	ONE_SECONDS	= 1000;
public	static boolean finished	= true;
private	CounterView counterValue;

public CounterController(int startValue, int endValue) {
  		this.startValue	= startValue;
		this.endValue= endValue;
		this.counterValue= new CounterView(startValue,endValue);
		Display();
     }

    public void CounterController(int startValue)
	{
		counterValue.setCounterValue(startValue);
		Display();
	}

    public static void main(String[] args) {
	int	startValue = 0;
	int	endValue = 0;
	boolean	dofile1	= true;
	String yn = "";


	Scanner	keyboard = new Scanner(System.in);

    do{
		System.out.println("This program will test a timer.");
		System.out.println("Enter a	start number of	seconds.");
		startValue = keyboard.nextInt();
		System.out.println("Enter an end number	of seconds.");
		endValue = keyboard.nextInt();
		CounterController counter = new CounterController(startValue, endValue);
		counter.start();

		while(finished){
			System.out.println("Time Is	: "	+ counter.getTime());
			counter.counterMode();
			try {
				Thread.sleep(ONE_SECONDS);
			}
			catch (InterruptedException	e) {
				e.printStackTrace();
			}

   		}

		System.out.println("Try again? (y/n)");
		yn = keyboard.next();

		if (yn.equalsIgnoreCase("n")) {
				dofile1	= false;
		} else if (yn.equalsIgnoreCase("y")){
				dofile1	= true;
				}

	}while	(dofile1);
}

}


public class CounterModel
{
	private	CounterView counterValue;
	public	static boolean finished	= true;
	private	int	endValue;
	private	int	startValue;


	public void	run(){}

	public void	counterMode()
	{
		if(counterValue.getValue() == endValue){
			finished = false;
			System.out.println("Timer is completed.");
		}else {
			counterValue.increment();
		if(counterValue.getValue() == 0) {
			counterValue.increment();
		}
		}
		Display();
	}

	public void setCounterValue(int startValue)
	{
		this.counterValue.setValue(startValue);
		Display();
	}

	public void	timeTick()
	{
		   counterValue.increment();
		if(counterValue.getValue() == 0) {
		   counterValue.increment();
		}
		Display();
	}

}



public class CounterView {

    private int endValue;
    private int startValue;
    private	String displayString;
    private	CounterView counterValue;

    public CounterView(int startValue, int endValue)
    {
        this.startValue = startValue;
        this.endValue = endValue;
    }

    /**
     * Return the current value.
     */
    public int getValue()
    {
        return startValue;
    }

	private	void Display()
	{
		displayString =	counterValue.getDisplayValue();
	}

	public String getTime()
	{
		return displayString;
	}

    public String getDisplayValue()
    {
        if(startValue < 10) {
            return "0" + startValue;
        }
        else {
            return "" + startValue;
        }

    }

    public void setValue(int replacementValue)
    {
        if((replacementValue >= 0) && (replacementValue < endValue)) {
            startValue = replacementValue;
        }
    }

    public void increment()
    {
        startValue = (startValue + 1); //% endSec;
    }

}

[John Jai]

Take one error at a time.

F:\Object Java\Assignments\Assignment 7\CounterController\src\CounterController.java:16: error: cannot find symbol
Display();
^
symbol: method Display()
location: class CounterController

It says the method named Display() is not present or not resolved in the class CounterController.

1. Check you have a method named Display() in the class you are using.

2. Do you wish to call a Display() method in the other classes CounterModel or CounterView?

3. If so is the method Display() is declared static or non-static.

4. If the Display() method is declared static you call it like classname.Display()

5. If the Display() method is non-static, you shall call it like object.Display(). So you have to create an object for the class first before invoking the method.
I think you intend to call the Display() method in the CounterView class - So it would be something like

CounterView cv = new CounterView(1, 3); // 1 & 3 are my custom dummy variables just to create an object...
cv.Display();

6. To make a method accessible outside the class, it should not be marked private. So change the access specifier from private to public for the method Display() in CounterView class.

And after resolving this error you can take up the next...

[Luke Stamper]

So this is my CounterController class (oh yeah, i'm down to three errors!!!)

I did what you suggested and created a new object (counter) of class CounterController, similar to what was done to get the Display() method to work, however, I am getting the errors....
I don't understand why the same strategy isn't working for these two methods.

--------------------Configuration: <Default>--------------------
F:\Object Java\Assignments\Assignment 7\CounterController\src\CounterController.java:46: error: cannot find symbol
System.out.println("Time Is : " + counter.getTime());
^
symbol: method getTime()
location: variable counter of type CounterController
F:\Object Java\Assignments\Assignment 7\CounterController\src\CounterController.java:47: error: cannot find symbol
counter.counterModel();
^
symbol: method counterModel()
location: variable counter of type CounterController
2 errors

Process completed.

import java.util.Scanner;

public class CounterController extends Thread{

private int startValue;
private int endValue;
public static final	int	ONE_SECONDS	= 1000;
public	static boolean finished	= true;
public	CounterView counterValue;

CounterModel cm = new CounterModel();
CounterView cv = new CounterView(startValue, endValue);

	public CounterController(int startValue, int endValue) {
  		this.startValue	= startValue;
		this.endValue= endValue;
		this.counterValue= new CounterView(startValue,endValue);
		cv.Display();
     }

    public void CounterController(int startValue)
	{
		cm.setCounterValue(startValue);
		cv.Display();
	}

    public static void main(String[] args) {
	int	startValue = 0;
	int	endValue = 0;
	boolean	dofile1	= true;
	String yn = "";

	Scanner	keyboard = new Scanner(System.in);

    do{
		System.out.println("This program will test a timer.");
		System.out.println("Enter a	start number of	seconds.");
		startValue = keyboard.nextInt();
		System.out.println("Enter an end number	of seconds.");
		endValue = keyboard.nextInt();
		CounterController counter = new CounterController(startValue, endValue);
		counter.start();

		while(finished){
			System.out.println("Time Is	: "	+ counter.getTime());
			counter.counterModel();
			try {
				Thread.sleep(ONE_SECONDS);
			}
			catch (InterruptedException	e) {
				e.printStackTrace();
			}

   		}

		System.out.println("Try again? (y/n)");
		yn = keyboard.next();

		if (yn.equalsIgnoreCase("n")) {
				dofile1	= false;
		} else if (yn.equalsIgnoreCase("y")){
				dofile1	= true;
				}

	}while	(dofile1);
}

}

[John Jai]

Now see below error -

F:\Object Java\Assignments\Assignment 7\CounterController\src\CounterController.java:46: error: cannot find symbol
System.out.println("Time Is : " + counter.getTime());
^
symbol: method getTime()
location: variable counter of type CounterController

You are calling the getTime() method using an instance created for the CounterController class. So do you have the getTime() method in the CounterController class?

Which class the getTime() method is present?

[John Jai]

My above post shall be used to resolve this error too -

F:\Object Java\Assignments\Assignment 7\CounterController\src\CounterController.java:47: error: cannot find symbol
counter.counterModel();
^
symbol: method counterModel()
location: variable counter of type CounterController

The method counterModel() is not present in the CounterController class.
But it's not present in CounterModel class too which I think you intend to call

[Luke Stamper]

John, thank you so much for helping me out.

I hope this is the last error...


--------------------Configuration: <Default>--------------------
This program will test a timer.
Enter a start number of seconds.
1
Enter an end number of seconds.
3
Exception in thread "main" java.lang.NullPointerException
at CounterView.Display(CounterView.java:33)
at CounterController.<init>(CounterController.java:19)
at CounterController.main(CounterController.java:42)

Process completed.

Looking through my code, I think the error has something to do with my counter object i created from the CounterController class.

[Luke Stamper]

I forgot to include my modified code...

import java.util.Scanner;

public class CounterController extends Thread{

private int startValue;
private int endValue;
public static final	int	ONE_SECONDS	= 1000;
public	static boolean finished	= true;
public	CounterView counterValue;

CounterModel cm = new CounterModel();
CounterView cv = new CounterView(startValue, endValue);

	public CounterController(int startValue, int endValue) {
  		this.startValue	= startValue;
		this.endValue= endValue;
		this.counterValue= new CounterView(startValue,endValue);
		cv.Display();
     }

    public void CounterController(int startValue)
	{
		cm.setCounterValue(startValue);
		cv.Display();
	}

    public static void main(String[] args) {
	int	startValue = 0;
	int	endValue = 0;
	boolean	dofile1	= true;
	String yn = "";

	Scanner	keyboard = new Scanner(System.in);

    do{
		System.out.println("This program will test a timer.");
		System.out.println("Enter a	start number of	seconds.");
		startValue = keyboard.nextInt();
		System.out.println("Enter an end number	of seconds.");
		endValue = keyboard.nextInt();
		CounterController counter = new CounterController(startValue, endValue);
		CounterView cv = new CounterView(startValue, endValue);
		CounterModel cm = new CounterModel();
		counter.start();

		while(finished){
			System.out.println("Time Is	: "	+ cv.getTime());
			cm.counterModel();
			try {
				Thread.sleep(ONE_SECONDS);
			}
			catch (InterruptedException	e) {
				e.printStackTrace();
			}

   		}

		System.out.println("Try again? (y/n)");
		yn = keyboard.next();

		if (yn.equalsIgnoreCase("n")) {
				dofile1	= false;
		} else if (yn.equalsIgnoreCase("y")){
				dofile1	= true;
				}

	}while	(dofile1);
}

}

[John Jai]

NullPointerException occurs when you try to do some operation on a reference that points to null. This is a Runtime Exception which you receive when you run your code.

Exception in thread "main" java.lang.NullPointerException
at CounterView.Display(CounterView.java:33)
at CounterController.<init>(CounterController.java:19)
at CounterController.main(CounterController.java:42)

The Exception says which line it has occurred - at CounterView.Display(CounterView.java:33) - it tells the Exception occurred at Display method in the CounterView class in the line # 33.
The other lines displayed beneath it is just a trace of the Exception and it leads to the line CounterController class's # 42...

So check the CounterView class in the line #33 which is the source of the NullPointerException. Can you tell which reference in that particular line might be pointing to null?

[Luke Stamper]

I think it has something to do with the counterValue not being instantiated in the CounterView class, but when I tried to remedy that, it did not work. I am not really sure if that is the problem, but looking at my code, I think I need something more to use the counterValue.getDisplayValue(); properly.

[Luke Stamper]

I figured it out! I had a friend shed some light on everything I was doing wrong and he helped me clean up my program. Thanks again for your help. I love the JavaRanch!

import java.util.Scanner;

public class CounterController extends Thread{

public static final	int	ONE_SECONDS	= 1000;
public	static boolean complete	= false;

public static CounterModel cm;
public static CounterView cv;

	public CounterController(int startValue, int endValue)
	{
     }

    public CounterController(int startValue)
	{
		cm.setStartValue(startValue);
	}

	public static void main(String[] args)
	{
		int	startValue = 0;
		int	endValue = 0;

		//initialize the view and model
		cm = new CounterModel();
		cv = new CounterView();

		boolean	dofile1	= true;
		boolean finished = false;
		String yn = "";

		Scanner	keyboard = new Scanner(System.in);

		while (dofile1)
		{
			System.out.println("This program will test a timer.");
			System.out.println("Enter a	start number of	seconds.");
			startValue = keyboard.nextInt();
			System.out.println("Enter an end number	of seconds.");
			endValue = keyboard.nextInt();

			// set model values
	  		cm.setStartValue(startValue);
			cm.setEndValue(endValue);

			do{
				cv.printTime(cm.getStartValue());

				try
				{
					Thread.sleep(ONE_SECONDS);
				}
				catch (InterruptedException	e)
				{
					e.printStackTrace();
				}

				if(cm.getStartValue() >= cm.getEndValue()){
					finished = true;
					System.out.println("Timer is completed.");
				}else{
					cm.increment();
				}


			}while(!finished);

			System.out.println("Try again? (y/n)");
			yn = keyboard.next();

			if (yn.equalsIgnoreCase("n"))
			{
				dofile1	= false;
			}
			else if (yn.equalsIgnoreCase("y"))
			{
				dofile1	= true;
				finished = false;
			}
			else
			{
				System.out.println("What kind of a choice is that?");
				System.out.println("The program will now close.");
				dofile1 = false;
			}
		}
    }
}



public class CounterModel
{
	private	int	endValue;
	private	int	startValue;

	public CounterModel(int startValue, int endValue)
	{
		setStartValue(startValue);
		setEndValue(endValue);
	}

	public CounterModel()
	{
		setStartValue(0);
		setEndValue(0);
	}

	public void setStartValue(int startValue)
	{
		this.startValue = startValue;
	}

	public void setEndValue(int endValue)
	{
		this.endValue = endValue;
	}

	public int getStartValue()
	{
		return startValue;
	}

	public int getEndValue()
	{
		return endValue;
	}

	public void	increment()
	{
		startValue++;
	}

}



public class CounterView {

    public CounterView() { }

	public void printTime(int curTime)
	{
		System.out.println("Time Is	: "	+ getDisplayValue(curTime));
	}

    public String getDisplayValue(int curTime)
    {
        if(curTime < 10) {
            return "0" + curTime;
        }
        else {
            return "" + curTime;
        }
    }

}