Exception Handling: Checked vs Unchecked

try-catch-finally, try-with-resources, throws, and custom exceptions

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Java distinguishes between Checked Exceptions (enforced by the compiler at build time, e.g. IOException) and Unchecked Exceptions (RuntimeException, e.g. NullPointerException).

Checked vs Unchecked & Try-With-Resources

Checked Exceptions: Subclasses of Exception (excluding RuntimeException). Must be caught in a try-catch block or declared with throws.

Unchecked Exceptions: Subclasses of RuntimeException. Caused by logic bugs; compiler does not force handling.

Try-With-Resources: Automatically closes classes implementing AutoCloseable (like file streams and database connections).

Try-With-Resources and Custom Exceptions

Try It Yourself »

class InsufficientFundsException extends Exception {
    public InsufficientFundsException(String msg) {
        super(msg);
    }
}

public class Bank {
    public static void withdraw(double balance, double amount) throws InsufficientFundsException {
        if (amount > balance) {
            throw new InsufficientFundsException("Cannot withdraw $" + amount + " from balance $" + balance);
        }
        System.out.println("Withdrawal approved!");
    }

    public static void main(String[] args) {
        try {
            withdraw(100.0, 150.0);
        } catch (InsufficientFundsException e) {
            System.err.println("Transaction Failed: " + e.getMessage());
        }
    }
}

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Test Yourself With Exercise

+15 XP

Which type of exception in Java is checked by the compiler at compile-time, requiring mandatory try-catch or a throws declaration?

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