exception-handling

Exception handling

What is exception handling?

• An exception is an unexpected event that disrupts normal program execution

• Exception handling is how a program detects and responds to these errors, allowing it to recover or shut down cleanly

Why use exception handling?

• Prevents programs from crashing unexpectedly

• Allows for user-friendly error messages

• Makes programs more robust and reliable

• Handles problems caused by:

  • Division by zero

  • File not found or end-of-file errors

  • Hardware or device failures (e.g. printers, lost connections)

  • Invalid input from users

Causes of exceptions

Pseudocode

TRY // Code that might cause an error OPEN "data.txt" FOR READ READ record FROM "data.txt" SET result = 10 / userInput
EXCEPT // Code to handle the error OUTPUT "An error occurred during file processing or division." CLOSE "data.txt"
ENDTRY

Key terms

Python

try: file = open("data.txt", "r") line = file.readline() user_input = int(input("Enter a number: ")) result = 10 / user_input print("Result:", result) file.close() except FileNotFoundError: print("Error: File not found.") except ZeroDivisionError: print("Error: Cannot divide by zero.") except Exception as e: print("An unexpected error occurred:", e) finally: try: file.close() except: pass # file might not have opened

Java

import java.io.*;
import java.util.Scanner; public class ExceptionHandlingExample { public static void main(String[] args) { BufferedReader reader = null; try { reader = new BufferedReader(new FileReader("data.txt")); String line = reader.readLine(); Scanner scanner = new Scanner(System.in); System.out.print("Enter a number: "); int userInput = scanner.nextInt(); int result = 10 / userInput; System.out.println("Result: " + result); } catch (FileNotFoundException e) { System.out.println("Error: File not found."); } catch (ArithmeticException e) { System.out.println("Error: Cannot divide by zero."); } catch (IOException e) { System.out.println("Error reading from file."); } catch (Exception e) { System.out.println("An unexpected error occurred: " + e.getMessage()); } finally { try { if (reader != null) { reader.close(); } } catch (IOException e) { // Ignore closing error } } }
}