Checked vs unchecked exceptions in Java - Practice Questions

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of code with checked exception handling

What is the output of this Java code snippet?

Java

import java.io.*;

public class Test {
    public static void main(String[] args) {
        try {
            throw new IOException("IO error");
        } catch (IOException e) {
            System.out.println("Caught checked exception");
        }
    }
}

A Compilation error: unhandled exception

B Caught unchecked exception

C Caught checked exception

D No output

💡 Hint

Think about how checked exceptions must be caught or declared.

IOException is a checked exception. The code catches it and prints the message.

❓ Predict Output

intermediate

Output of code with unchecked exception

What happens when this Java code runs?

Java

public class Test {
    public static void main(String[] args) {
        throw new NullPointerException("Null pointer");
    }
}

A Program throws NullPointerException and terminates

B Program prints "Null pointer"

C Compilation error: unhandled exception

D Program runs without output

💡 Hint

Unchecked exceptions do not need to be caught or declared.

NullPointerException is unchecked and not caught, so the program terminates with the exception.

🧠 Conceptual

advanced

Difference between checked and unchecked exceptions

Which statement correctly describes the difference between checked and unchecked exceptions in Java?

A Neither checked nor unchecked exceptions require catching or declaring.

B Unchecked exceptions must be caught or declared; checked exceptions do not require this.

C Both checked and unchecked exceptions must always be caught or declared.

D Checked exceptions must be caught or declared; unchecked exceptions do not require this.

💡 Hint

Think about compiler enforcement for exception handling.

Checked exceptions are checked at compile time and must be handled or declared. Unchecked exceptions are not checked at compile time.

❓ Predict Output

advanced

Compilation error due to unchecked exception declaration

What error occurs when compiling this Java code?

Java

public class Test {
    public static void main(String[] args) throws NullPointerException {
        throw new NullPointerException("Error");
    }
}

A Compilation error: cannot declare unchecked exception in throws clause

B Compiles and runs, throws NullPointerException

C No output, program runs normally

D Compilation error: unhandled exception

💡 Hint

Consider if declaring unchecked exceptions in throws clause is allowed.

Declaring unchecked exceptions in throws clause is allowed but not required. The code compiles and throws the exception at runtime.

❓ Predict Output

expert

Output and exception behavior with mixed checked and unchecked exceptions

What is the output when running this Java program?

Java

import java.io.IOException;

public class Test {
    public static void riskyMethod() throws IOException {
        if (false) {
            throw new IOException("Checked IO error");
        } else {
            throw new IllegalArgumentException("Unchecked argument error");
        }
    }

    public static void main(String[] args) {
        try {
            riskyMethod();
        } catch (IOException e) {
            System.out.println("Caught checked exception");
        }
    }
}

A Program terminates with IllegalArgumentException

B Caught checked exception

C Compilation error: unhandled exception

D No output

💡 Hint

Consider which exceptions are caught and which are not.

The method may throw IOException (checked) or IllegalArgumentException (unchecked). Only IOException is caught. If unchecked exception occurs, program terminates.