Chapter 9, Problem 9PP

Lap Timer using Applet

Program Plan:

Filename: “LapTimerApplication.java”

• Import the required packages.
• Declare the class “LapTimerApplication”.
  • Declare the required variables.
  • Define the constructor.
    • Set the window size
    • Close the window.
    • Create an object for “Container” class.
    • Initially set the background color as white.
    • Set the layout.
    • Create the buttons.
    • Add the action to these buttons.
    • Add the buttons on the window screen.
    • Create the object for the labels.
    • Add the label on the window screen.
    • Create an object for the “LapTimer” class.
  • Declare the “actionPerformed” method.
    • Declare the required variables with the values.
    • If the action command is start, then execute the “if” condition.
      • Inside the “try” block, call the method “start ()” and set the labels.
      • In catch block, set the error message.
        • If the action command is lap, then execute the “if” condition.
        • • Inside the “try” block, call the method “markLap ()” and set the labels.
          • In catch block, set the error message.
  • Declare the “main ()” method.
    • Create an object for “LapTimer” class.
    • Show the window.

Filename: “LapTimer.java”

• Import required package
• Define the class “LapTimer”.
  • Declare required private variables “running”, “startTime”, “lapStart”, “lapTime”, “totalTime”, “lapsCompleted”, “lapsInRace”.
  • Define the constructor.
    • Assign the values.
  • Define the method “start ()”.
    • Check the condition “running == true || lapsCompleted > 0”.
      • Throw “TimerException” exception with a message.
        • Assign “true” to the variable “running”.
        • Calculate the value of “startTime”.
        • Assign the value of “startTime” to “lapStart”.
  • Define the method “markLap ()”.
    • Check if value of “running” is “false”.
      • Check if laps completed are equal to 0.
        • Throw “”TimerException exception with a message.
        • • Increment the value of “lapsCompleted”.
          • Get the current time and store it in a variable “currentTime”.
          • Calculate “lapTime” by subtracting “lapStart” from “currentTime”.
          • Calculate “totalTime” by subtracting “startTime” from “currentTime”.
          • Assign the value of “currentTime” to “lapStart”.
          • Check if the value of “lapsCompleted” and “lapsInRace” are equal.
            • Assign “false” to “running”.
  • Define the method “getLapTime ()”.
    • Check if “lapsCompleted” is 0.
      • Throw “”TimerException exception with a message.
        • • Return “lapTime”.
  • Define the method “getTotalTime ()”.
    • Check if “lapsCompleted” is 0.
      • Throw “”TimerException exception with a message.
        • • Return “totalTime”.
  • Define the method “getLapsRemaining ()”.
    • Return the value.
  • Define the “main ()” function.
    • Declare a variable and assign it with a value.
    • Create an object for the class “LapTimer”.
    • Call the function “start ()”.
    • Call the function “markLap ()”.
    • Print the number of laps.
    • Print the lap time by calling the function “getLapTime ()”.
    • Print the total time by calling the function “getTotalTime ()”.
    • Print the remaining number of laps by calling the function “getLapsRemaining ()”.

Filename: “TimerException.java”

• Define an exception class named “TimerException”.
  • Define a parameterized constructor for the class.
    • Call the parent class’s method by passing a message.