Chapter 6: Print Calendar - Method Abstraction and Stepwise Refinement

📅 What We're Building This Week (Week 11)

Note: The link to this repository must be turned in no later than the end of the week on Friday, November 7 @ 11:59 p.m.

A calendar application that:

• Asks the user for a year and a month
• Prints a formatted calendar for that month

Example Output:

Enter full year (e.g., 2012): 2025
Enter month as a number between 1 and 12: 11

 November 2025
-----------------------------
 Sun Mon Tue Wed Thu Fri Sat
                          1
   2   3   4   5   6   7   8
   9  10  11  12  13  14  15
  16  17  18  19  20  21  22
  23  24  25  26  27  28  29
  30

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🎯 Learning Objectives

By the end of this activity, you'll understand:

• Method Abstraction: Breaking complex problems into smaller, manageable pieces
• Stepwise Refinement: Top-down design and bottom-up implementation
• Code Reusability: Writing methods that can be used multiple times
• Modular Programming: Making code easier to read, debug, and test

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🧩 The Big Picture: Breaking Down the Problem

Level 1: The Main Problem

Print a calendar for a given month and year

Level 2: Two Main Tasks

1. Get input from the user (year and month)
2. Print the calendar for that month

Level 3: Breaking Down "Print Calendar"

The printMonth method needs to:

• Print the month title (month name, year, and day headers)
• Print the month body (the actual dates)

Level 4: Breaking Down "Print Month Title"

• Get the month name (convert number to string like "November")

Level 5: Breaking Down "Print Month Body"

• Get the start day of the week (is the 1st a Sunday? Monday?)
• Get the number of days in the month (28, 29, 30, or 31?)

Level 6: Breaking Down "Get Start Day"

• Calculate the total number of days since a known reference date

Level 7: Breaking Down "Get Total Days"

• Determine if a year is a leap year
• Get the number of days in each month

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🏗️ Implementation Strategy: Bottom-Up Approach

We'll build from the bottom up, starting with the smallest helper methods and working our way up to the main program.

Implementation Order:

1. ✅ isLeapYear - The foundation (we did this in Chapter 3!)
2. ✅ getNumberOfDaysInMonth - Uses isLeapYear
3. ✅ getTotalNumberOfDays - Uses the above two methods
4. ✅ getStartDay - Uses getTotalNumberOfDays
5. ✅ getMonthName - Converts month number to name
6. ✅ printMonthTitle - Uses getMonthName
7. ✅ printMonthBody - Uses getStartDay and getNumberOfDaysInMonth
8. ✅ printMonth - Uses printMonthTitle and printMonthBody
9. ✅ main - Puts it all together!

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📝 Key Concepts to Remember

Reference Date

• January 1, 1800 was a Wednesday (day 3 of the week, where Sunday = 0)
• We calculate all dates relative to this known point

Days in Each Month

• 31 days: January, March, May, July, August, October, December
• 30 days: April, June, September, November
• 28/29 days: February (depends on leap year)

Leap Year Rules

A year is a leap year if:

• It's divisible by 400, OR
• It's divisible by 4 AND NOT divisible by 100

Examples:

• 2000 = leap year (divisible by 400)
• 2024 = leap year (divisible by 4, not by 100)
• 1900 = NOT a leap year (divisible by 100, but not 400)

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🚀 Getting Started

1. Open the file F25_PrintCalendar_FirstName_LastName.java
2. Replace FirstName_LastName with your actual name
3. Follow along with the instructor or video
4. Complete each TODO section as we work through it together
5. Test your program frequently!

Testing Your Program

After completing each method, you can test it by:

• Uncommenting the test code in main
• Running the program
• Verifying the output matches expected results

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💡 Tips for Success

1. Work step-by-step: Don't try to write everything at once
2. Test frequently: After writing each method, test it!
3. Use the textbook: This follows the example exactly
4. Ask questions: If you're stuck, raise your hand or ask in chat
5. Collaborate: Discuss with classmates, but write your own code
6. Think about reusability: Notice how we use smaller methods in bigger ones

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🎓 Benefits of This Approach

Simpler Program

• Each method has ONE clear purpose
• Easy to read and understand

Code Reusability

• Methods like isLeapYear and getNumberOfDaysInMonth are used multiple times
• No redundant code!

Easier Development & Debugging

• Test one method at a time
• If something breaks, you know exactly where to look

Better Teamwork

• Different programmers could work on different methods
• As long as the method signatures match, everything works together

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📚 Additional Resources

• Textbook: Chapter 6 - Methods
• Lecture slides (provided in class)
• Previous class video recording
• Java API Documentation: Scanner

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Remember: Programming is a skill that improves with practice. Work through this carefully, and you'll understand how professional programmers break down complex problems into manageable pieces! 🌟