Eric Spencer

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Free Time Calculator in Java

A Java program to find overlapping free time for up to four people.

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Overview

This project finds overlapping free time in people's schedules.

How it works

1. Enter availability for a given day (for example, 4-6pm and 8-10pm).
2. Enter a second person's availability (for example, 5-9pm).
3. The program prints a time spreadsheet and calculates when everyone is available.
4. It works for up to four people at once.

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Workings and caveats

• A 2-D array holds the schedules the users provide.
• AM/PM time conversion, 10, 11 and 12 in particular, was the hard part.
• Coded entirely inside a JVM.

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Demo video

The source code was lost, because it lived on a school virtual machine. A sample run of the program was recorded: Watch on YouTube.

Watch on YouTube

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Recreation

A recreation by ChatGPT, without the user experience of the original:

import java.util.*;

public class FreeTimeCalculator {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        boolean[] timeSlots = new boolean[24]; // each hour of the day

        Arrays.fill(timeSlots, true); // Start with all available

        for (int person = 1; person <= 4; person++) {
            System.out.println("Enter availability for Person " + person + " (e.g., 4-6,8-10 or 'x' to skip): ");
            String input = scanner.nextLine();
            if (input.equalsIgnoreCase("x")) break;

            boolean[] personSlots = new boolean[24];
            Arrays.fill(personSlots, false);

            String[] ranges = input.split(",");
            for (String range : ranges) {
                String[] hours = range.split("-");
                int start = Integer.parseInt(hours[0].trim());
                int end = Integer.parseInt(hours[1].trim());
                for (int i = start; i < end; i++) {
                    personSlots[i] = true;
                }
            }

            for (int i = 0; i < 24; i++) {
                timeSlots[i] = timeSlots[i] && personSlots[i];
            }
        }

        System.out.println("\nShared Free Time:");
        boolean found = false;
        for (int i = 0; i < 24; i++) {
            if (timeSlots[i]) {
                System.out.print(i + ":00 ");
                found = true;
            }
        }
        if (!found) {
            System.out.println("No common availability.");
        }
    }
}