Java Bootcamp – Workbooks and Challenges
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Contacts – Part 1

From Java Bootcamp Resources -> Module 2 -> 8. Exception Handling -> Exception Handling Workbooks, open the folder: contacts.

Requirements.


Based on the requirements, there are two types of objects:

We can describe each contact using four fields: name, age, birth date and phone number.

The contact manager is identified by the contacts that it manages. It also performs the actions of adding/removing contacts.

The tasks in this workbook apply to the Contact class.

Task 1 – Fields


Add the necessary fields to the Contact class. Protect each field using the private keyword.

Task 2 – Research


The constructor will only receive three parameters: name, phoneNumber and birthDate.

The birthDate that gets passed will automatically determine the age. Use the hints below to write code that mimics this process:

HINTS:

  1. Research how to create an object of the SimpleDateFormat class.

  2. Use the SimpleDateFormat object to parse() a Date from the birthDate String.

    • Assume the birthDate follows the MM/dd/yyyy format.
  3. Get the current time as a Date object.

  4. Find a method from the Date class that returns milliseconds since 1970 from each date.

  5. Get the difference between both time units. This difference is the person's age in milliseconds.

  6. Research how to use the TimeUnit class to convert from milliseconds to days. Then, divide by 365 to get the years.

  7. Typecast the result to int and update the age field.

IMPORTANT:

  • The parse method from SimpleDateFormat throws a checked exception.

  • It's the caller's job to handle the failure. But, do not try-catch inside the constructor.

  • Instead, throw the exception from the constructor so that whoever is calling it handles the failure.

Task 3 – Import Contact


At the very top , you'll notice the line: package models;. This line specifies the folder that Contact is in.

Inside Main.java, write import <folder name>.<class name>; to import the class. Note, you can autocomplete this step in Visual Studio Code.

Task 4 – Test your code.

  1. Inside main(), try to create a new object of the Contact class.

  2. If there's a failure, catch it and print its message.

  3. Add a finally block that prints: Process Complete

Example output for the birthday: "07/23/1912":

Task 5 – Research (again)

If the caller passes a month of 34347, it should throw a ParseException. But unless you tell the date formatter to not be "lenient", it will use heuristics and falsely interpret the input.

Example output for a month of 34347:

So, research how to stop the formatter from being "lenient". The date String must strictly adhere to the format MM/dd/yyyy.

Hints:

  • In the documentation, look for a method that can specify whether date parsing should be lenient.

  • You may also look for a similar question on Stack-Overflow.

Final output:

>>: Unparseable date: "34347/23/1912"

>>: Process Complete

Good Luck!


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