Exception Handling

        
          import java.io.*;
import java.util.Scanner;

public class ExceptionHandlingDemo {
    public static void main(String[] args) {
        try {
            // Multiple operations that might throw exceptions
            readFile("example.txt");
            divideNumbers(10, 0);
            processArray(null);

        } catch (FileNotFoundException e) {
            System.out.println("File not found: " + e.getMessage());
        } catch (ArithmeticException e) {
            System.out.println("Math error: " + e.getMessage());
        } catch (NullPointerException e) {
            System.out.println("Null pointer: " + e.getMessage());
        } catch (Exception e) {
            // Catch-all for unexpected exceptions
            System.out.println("Unexpected error: " + e.getMessage());
        } finally {
            // Always executed
            System.out.println("Cleanup completed");
        }

        // Try-with-resources (Java 7+)
        try (Scanner scanner = new Scanner(System.in);
             FileWriter writer = new FileWriter("output.txt")) {

            System.out.print("Enter your name: ");
            String name = scanner.nextLine();
            writer.write("Hello, " + name + "!");

        } catch (IOException e) {
            System.out.println("IO Error: " + e.getMessage());
        }
    }

    // Method that throws checked exception
    public static void readFile(String filename) throws FileNotFoundException {
        File file = new File(filename);
        Scanner scanner = new Scanner(file);

        while (scanner.hasNextLine()) {
            System.out.println(scanner.nextLine());
        }
        scanner.close();
    }

    // Method that throws unchecked exception
    public static int divideNumbers(int a, int b) {
        if (b == 0) {
            throw new ArithmeticException("Division by zero");
        }
        return a / b;
    }

    // Method that might throw NullPointerException
    public static void processArray(String[] array) {
        if (array == null) {
            throw new NullPointerException("Array cannot be null");
        }
        System.out.println("Array length: " + array.length);
    }
}

// Custom exception class
class InvalidAgeException extends Exception {
    public InvalidAgeException(String message) {
        super(message);
    }
}

class PersonValidator {
    public static void validateAge(int age) throws InvalidAgeException {
        if (age < 0) {
            throw new InvalidAgeException("Age cannot be negative");
        }
        if (age > 150) {
            throw new InvalidAgeException("Age seems unrealistic");
        }
    }

    public static void main(String[] args) {
        try {
            validateAge(-5);
        } catch (InvalidAgeException e) {
            System.out.println("Validation error: " + e.getMessage());
        }
    }
}