Understanding Exceptions
Definition
Exceptions
Unusual or unexpected events that disrupt the normal flow of a program.
Exceptions can help with:
- Input validation: Ensuring data is in the correct format and within acceptable ranges.
- Resource availability: Checking if files, databases, or network connections are accessible.
- Logical errors: Handling cases where the logic does not cover all possibilities.
Note
The term "exception" in this context refers to cases that deviate from the general rule, not just runtime errors.
Why Exceptions Matter
- Robustness: Handling exceptions ensures that programs can gracefully recover from unexpected situations.
- Reliability: Anticipating exceptions reduces the likelihood of crashes or incorrect results.
- User Experience: Clear error messages and recovery options improve usability.
Identifying Exceptions in Problem Solutions
Hint
- When designing a solution, always ask: "What could go wrong?"
- This mindset helps identify potential exceptions early.
- Analyse the problem: Break down the problem into smaller components and identify potential failure points.
- Consider edge cases: Think about unusual or extreme inputs that might cause errors.
- Define pre-conditions: Specify conditions that must be true before executing a procedure.
- Plan for post-conditions: Ensure the desired outcome is achieved, even if exceptions occur.
Analogy
- Think of exceptions like potholes on a road.
- Identifying them in advance allows you to plan detours, ensuring a smooth journey.
Example
Consider a company policy for calculating bonuses:
- Worked 9 months or more: bonus = 30% of monthly salary
- Worked less than 9 months:
- Salary $<$ €2000: bonus = 20% of monthly salary
- Salary $\geq$ €2000: bonus = 10% of monthly salary
Exceptions to Consider:
- Missing data: What if the number of months worked is not provided?
- Invalid input: What if the salary is negative?
- Edge cases: What if an employee worked exactly 9 months?
Strategies for Handling Exceptions
- Anticipate and plan: Identify potential exceptions during the design phase.
- Use conditional statements: Implement logic to handle different scenarios.
- Provide meaningful feedback: Display clear error messages to guide users.
- Test thoroughly: Use unit tests and edge cases to ensure robustness.
Self review
- What is an exception in programming?
- How can exceptions help with input validation?
- Give examples of situations where exceptions help manage resource availability.
- Why is handling logical errors important in programs?
