Write a class LapTimer that can be used to time the laps in a race. The class sh

Question

Write a class LapTimer that can be used to time the laps in a race. The class should have the following private attributes: running-a boolean indication of whether the timer is running startTime-the time when the timer started lapStart-the timer's value when the current lap started lapTime-the elapsed time for the last lap total Time-the total time from the start of the race through the last completed lap lapsCompleted-the number of laps completed so far lapsInRace-the number of laps in the race The class should have the following methods: LapTimer(n)-a constructor for a race having n laps. start-starts the timer. Throws an exception if the race has already started. markLap-marks the end of the current lap and the start of a new lap. Throws an exception if the race is finished. getLapTime-returns the time of the last lap. Throws an exception if the first lap has not yet been completed. getTotalTime-returns the total time from the start of the race through the last completed lap. Throws an exception if the first lap has not yet been completed. getLapsRemaining-returns the number of laps yet to be completed, including the current one. Express all times in seconds. To get the current time in milliseconds from some baseline date, invoke Calendar. getInstance().getTimeInMi11is() This invocation returns a primitive value of type long. By taking the difference between the returned values of two invocations at two different times, you will know the elapsed time in milliseconds between the invocations. Note that the class Calendar is in the package java.

Explanation / Answer

Only the worker class is provided. So it will compile but not run as it doesn't have a main()

Program:

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import java.util.Calendar;

class LapTimer
{
    private boolean running;
    private long startTime;
    private long lapStart;
    private long lapTime;
    private long totalTime;
    private int lapsCompleted;
    private int lapsInRace;

    LapTimer(int n)
    {
        lapsInRace=n;
    }
    public void start()throws CustomException
    {
        if(startTime!=0)throw new CustomException("The match has already started!!");
        else startTime= Calendar.getInstance().getTimeInMillis();
        running=true;
    }
    public void markLap()
    {
        lapTime=Calendar.getInstance().getTimeInMillis();
        lapsCompleted++;
    }
    public long getTotalTime()
    {
        return totalTime;
    }
    public int getLapsRemaing()
    {
        return lapsInRace-lapsCompleted;
    }
}

class CustomException extends Exception
{
    String str;
    CustomException(String s)
    {
        str=s;
    }
    @Override
    public String toString()
    {
        return str;
    }
}

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