Exception Handling in Java

What is Exception Handling?

Exception handling is a mechanism in Java that allows us to handle runtime errors so the program does not terminate abruptly.

It helps to:

• Prevent program crash
• Maintain normal flow
• Improve user experience

What is an Exception?

An exception is an unwanted event that occurs during program execution and disrupts the normal flow of the program.

Example:

• Dividing a number by zero
• Accessing an invalid array index
• Opening a file that doesn’t exist

Types of Exceptions in Java

Java exceptions are mainly divided into:

1️⃣ Checked Exceptions

• Checked at compile time
• Must be handled
• Example: IOException, SQLException

2️⃣ Unchecked Exceptions

• Occur at runtime
• Not mandatory to handle
• Example: ArithmeticException, NullPointerException

⚙️ Exception Handling Keywords

Java provides 5 main keywords:

• try
• catch
• finally
• throw
• throws

Basic Syntax

try {
    // risky code
} catch (ExceptionType e) {
    // handling code
} finally {
    // always executes
}

1️⃣ try Block

The try block contains the risky code — code that may cause an exception.

👉 If an exception occurs inside try, it will immediately stop executing and jump to catch block.

2️⃣ catch Block

The catch block handles the exception.

👉 It prevents the program from crashing.

If exception occurs:

• Control moves from try → catch
• Error is handled
• Program continues

3️⃣ finally Block

The finally block always executes.

👉 Whether exception occurs or not
👉 Whether catch handles it or not

Used for:

• Closing files
• Closing database connections
• Cleaning resources

Example: Handling ArithmeticException

public class Main {
    public static void main(String[] args) {

        try {
            int a = 10;
            int b = 0;
            int result = a / b;
            System.out.println(result);
        } catch (ArithmeticException e) {
            System.out.println("Cannot divide by zero!");
        }

        System.out.println("Program continues...");
    }
}

Difference Between throw and throws

throw

• Used inside method
• Throws single exception
• Followed by object

throws

• Used in method declaration
• Declares multiple exceptions
• Followed by class name

Example:

throw new ArithmeticException("Error");

void test() throws IOException {
}

What Happens If Exception Is Not Handled?

If an exception is not handled:

• Program terminates immediately
• JVM prints stack trace
• Remaining code will not execute
• This is called abnormal termination.