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Exceptions and Validation

The School Enrollment System relies heavily on input validation and defensive programming to ensure data integrity and prevent runtime crashes.
Validation is centralized primarily in the Helpers class, while entity classes enforce basic structural rules through setters.

Purpose

The validation and exception‑handling system is designed to:

  • Prevent invalid data from entering the system
  • Protect the application from crashes caused by user input
  • Ensure consistent formatting of user information
  • Provide clear feedback when errors occur
  • Maintain clean separation between validation logic and business logic

This approach keeps the system stable and predictable.

Centralized Validation in Helpers

Most validation is performed through dedicated methods in the Helpers class.

Key validation methods

  • ValidatePassword
  • ValidateEmail
  • ValidatePhoneNumber
  • ValidateAddress
  • ValidateName

Each method checks for:

  • Non‑empty input
  • Minimum length requirements
  • Basic formatting rules
  • Logical correctness (e.g., phone number must be 10 digits)

These methods return true or false, allowing workflows to loop until valid input is provided.

Safe Integer Input

Method: getSafeIntInput

This method prevents crashes caused by invalid numeric input.

Behavior:

  1. Prompts the user for an integer
  2. Catches invalid input using exception handling
  3. Clears the scanner buffer
  4. Repeats until a valid integer is entered

This ensures that menus and numeric fields never break the program.

Role Validation

Method: checkValidityOfRole

Ensures that the user selects a valid role:

  • Student
  • Instructor
  • Admin

Invalid selections trigger a retry loop.

Field Updating with Predicates

Method: updateFieldWithPrompt

This method uses a Predicate<String> to validate new field values.

Advantages:

  • Reusable for any field
  • Clean separation between validation and updating
  • Eliminates repetitive code

Example fields validated through this method:

  • Email
  • Password
  • Phone number
  • Address

User Creation Validation

Method: createUserWithPrompt

Used when creating new students or instructors.

Behavior:

  • Prompts for a required field
  • Validates using a predicate
  • Repeats until valid input is provided

This ensures that all new users are created with valid data.

Entity‑Level Validation

Some validation is also performed inside entity classes such as Course.

Examples:

  • Course name and code must not be empty
  • Capacity must be positive
  • Credit hours must be greater than zero

Invalid values trigger error messages and do not update the field.

This prevents corrupted course data.

Exception Handling Philosophy

The system uses exceptions primarily for:

  • Input mismatch errors
  • File handling errors
  • Unexpected runtime issues

Design principles:

  • Never allow the program to crash due to user input
  • Always provide clear, user‑friendly error messages
  • Keep exception handling localized to the point of failure
  • Avoid exposing stack traces to the user

This ensures a smooth and predictable user experience.

Summary

The validation and exception‑handling system is a critical part of the School Enrollment System.
By centralizing validation in the Helpers class, enforcing structural rules in entity classes, and using safe input techniques, the system maintains data integrity and prevents crashes.

This design ensures that all workflows operate reliably and consistently.