Exception Handling

Question 1

What is an exception?

Answer 1

An exception is an error message.

Question 2

What are the two types of Exceptions?

Answer 2

Checked and Unchecked Exceptions

Question 3

What is a checked exception?

Answer 3

This is a compile time error, that the compiler forces you to handle with the use try/catch blocks and the throw/throws keywords.

Question 4

List 3 Examples of checked exceptions.

Answer 4

1. IOException
2. FileNotFoundException
3. SQLException

Question 5

What is an unchecked exception?

Answer 5

These are errors or exception that occur at runtime

Question 6

What are some examples of unchecked exceptions?

Answer 6

ArithmeticException
ArrayIndexOutOFBoundsException
NullPionterException

Question 7

Desing and test a custom exception in Java.

Answer 7

Custom Exception:

public class InvalidBookIdException extends Exception {
public InvalidBookIdException(String message) {
super(message);
}
}

testing:
import java.util.HashMap;
import java.util.Map;

public class Library {
private Map<String, String> books = new HashMap<>();

public Library() {
    books.put("B001", "Java Programming");
    books.put("B002", "Data Structures");
}

public String getBookById(String id) throws InvalidBookIdException {
    if (!books.containsKey(id)) {
        throw new InvalidBookIdException("Book ID " + id + " not found.");
    }
    return books.get(id);
} }