Step by Step solution about How to resolve the algorithm Nautical bell step by step in the Java programming language

The given Java code is a program that simulates a nautical bell that strikes every 30 minutes, with the number of strikes increasing by one each time, up to a maximum of eight strikes. The program runs indefinitely, striking the bell at the correct times according to the UTC time zone.

Here's a detailed explanation of the code:

1. Importing Libraries: The code begins by importing the necessary libraries.

   • DateFormat and SimpleDateFormat are used for formatting and displaying the current time.
   • TimeZone is used to specify the time zone for the program.

2. Main Method: The main method is the entry point of the program.

   • It creates an instance of the NauticalBell class, sets it as a daemon thread, and starts it.
   • The program then waits for the NauticalBell thread to finish before exiting.

3. NauticalBell Class: The NauticalBell class extends the Thread class and implements the run method.

   • The run method is the main logic for the program.
   • It initializes a DateFormat object with the format "HH:mm:ss" and sets the time zone to UTC.

4. Initializing Variables:

   • The number of bell strikes (numBells) is initialized to 0.
   • The current time (time) is obtained using System.currentTimeMillis().
   • The next bell strike time (next) is calculated by subtracting the remainder of time divided by (24 hours * 60 minutes * 60 seconds * 1000 milliseconds) from time. This effectively sets next to the upcoming midnight.

5. Calculating the Initial Number of Bell Strikes:

   • The program calculates the initial number of bell strikes (numBells) based on the time elapsed since midnight.
   • It increments numBells by 1 and takes the remainder when dividing by 8 to ensure it stays within the range of 1 to 8.

6. Main Loop:

   • The program enters an infinite loop to continuously strike the bell every 30 minutes.
   • Inside the loop, it calculates the wait time (wait) until the next bell strike.
     • If the current time (time) is greater than or equal to the next bell strike time (next), it prints the current time and number of bell strikes.
     • It then updates next to the next bell strike time and calculates the updated wait time.
     • Finally, it increments numBells by 1 and takes the remainder when dividing by 8 to keep it within the range of 1 to 8.
   • The thread sleeps for the calculated wait time before continuing the loop.

7. Exception Handling:

   • The try-catch block inside the loop handles InterruptedException that may occur when the thread is interrupted while sleeping.
   • If an interrupt occurs, the program exits the loop and terminates.

The Java program you provided implements a nautical bell, which rings every 30 minutes according to the ship's time. The program creates a thread, sets it as a daemon thread, and starts it. The thread then enters a while loop, which runs until the thread is interrupted. In the loop, the thread calculates the current time and the time of the next bell ringing. If the current time is greater than or equal to the next bell ringing time, the thread prints the current time and the number of bells that should be rung. The thread then updates the next bell ringing time and waits until the next bell ringing time. If the thread is interrupted, it returns from the run method and the program terminates.

Details:

• The NauticalBell class extends the Thread class, so it can be run as a separate thread.
• The main method creates a NauticalBell object, sets it as a daemon thread, and starts it.
• The run method of the NauticalBell class is the main entry point for the thread.
• The DateFormat class is used to format the current time as a string.
• The SimpleDateFormat class is a concrete implementation of the DateFormat class.
• The TimeZone class is used to specify the time zone for the DateFormat class.
• The numBells variable stores the number of bells that should be rung.
• The time variable stores the current time in milliseconds since the epoch.
• The next variable stores the time of the next bell ringing in milliseconds since the epoch.
• The while loop runs until the next variable is greater than or equal to the time variable.
• The if statement inside the loop checks if the time variable is greater than or equal to the next variable.
• If the time variable is greater than or equal to the next variable, the thread prints the current time and the number of bells that should be rung.
• The next variable is then updated to the time of the next bell ringing.
• The wait variable is set to the amount of time that the thread should wait until the next bell ringing time.
• The thread then sleeps for the amount of time specified by the wait variable.
• If the thread is interrupted while it is sleeping, it returns from the run method and the program terminates.

import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.TimeZone;

public class NauticalBell extends Thread {

    public static void main(String[] args) {
        NauticalBell bells = new NauticalBell();
        bells.setDaemon(true);
        bells.start();
        try {
            bells.join();
        } catch (InterruptedException e) {
            System.out.println(e);
        }
    }

    @Override
    public void run() {
        DateFormat sdf = new SimpleDateFormat("HH:mm:ss");
        sdf.setTimeZone(TimeZone.getTimeZone("UTC"));

        int numBells = 0;
        long time = System.currentTimeMillis();
        long next = time - (time % (24 * 60 * 60 * 1000)); // midnight

        while (next < time) {
            next += 30 * 60 * 1000; // 30 minutes
            numBells = 1 + (numBells % 8);
        }

        while (true) {
            long wait = 100L;
            time = System.currentTimeMillis();
            if (time - next >= 0) {
                String bells = numBells == 1 ? "bell" : "bells";
                String timeString = sdf.format(time);
                System.out.printf("%s : %d %s\n", timeString, numBells, bells);
                next += 30 * 60 * 1000;
                wait = next - time;
                numBells = 1 + (numBells % 8);
            }
            try {
                Thread.sleep(wait);
            } catch (InterruptedException e) {
                return;
            }
        }
    }
}