Java Exception Class

Introduction

The Exception class in Java is the root class for handling exceptions. It represents errors that can occur during the execution of a program, allowing you to manage these situations gracefully.

Table of Contents

1. What is Exception?
2. Types of Exceptions
3. Handling Exceptions
4. Examples of Exception Handling
5. Conclusion

1. What is Exception?

Exception is the superclass for all exceptions in Java, indicating conditions that a reasonable application might want to catch. It is part of Java’s exception handling mechanism.

2. Types of Exceptions

• Checked Exceptions: Must be caught or declared in the method signature (e.g., IOException, SQLException).
• Unchecked Exceptions: Also known as runtime exceptions, they do not need to be declared or caught (e.g., NullPointerException, ArithmeticException).

3. Handling Exceptions

To handle exceptions, use a try-catch block. The try block contains code that might throw an exception, while the catch block handles the exception.

4. Examples of Exception Handling

Example 1: Handling a Checked Exception

This example demonstrates handling a FileNotFoundException.

import java.io.File;
import java.io.FileNotFoundException;
import java.util.Scanner;

public class CheckedExceptionExample {
    public static void main(String[] args) {
        try {
            File file = new File("example.txt");
            Scanner scanner = new Scanner(file);
            while (scanner.hasNextLine()) {
                System.out.println(scanner.nextLine());
            }
            scanner.close();
        } catch (FileNotFoundException e) {
            System.out.println("Error: File not found.");
        }
    }
}

Output:

Error: File not found.

Example 2: Handling an Unchecked Exception

Here, we handle an ArithmeticException.

public class UncheckedExceptionExample {
    public static void main(String[] args) {
        try {
            int result = 10 / 0;
            System.out.println("Result: " + result);
        } catch (ArithmeticException e) {
            System.out.println("Error: Division by zero.");
        }
    }
}

Output:

Error: Division by zero.

Example 3: Using finally

This example shows how to use the finally block to execute code regardless of whether an exception occurs.

public class FinallyExample {
    public static void main(String[] args) {
        try {
            int[] numbers = {1, 2, 3};
            System.out.println(numbers[5]);
        } catch (ArrayIndexOutOfBoundsException e) {
            System.out.println("Error: Array index out of bounds.");
        } finally {
            System.out.println("Execution complete.");
        }
    }
}

Output:

Error: Array index out of bounds.
Execution complete.

Conclusion

The Exception class in Java is crucial for handling errors and exceptions in a controlled manner. By using try-catch blocks and managing exceptions effectively, you can create robust and error-resistant Java applications.