MCQs on Error Handling and Debugging | Scala

Get a deep understanding of error handling and debugging in Scala. This set of MCQs covers topics like Try, Success, Failure, catching exceptions, and debugging essentials.

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Error Handling and Debugging in Scala

1. Try, Success, Failure

1. What is the purpose of Try in Scala?
   • A) To catch and handle exceptions
   • B) To execute code in a safe way that can return a success or failure
   • C) To throw exceptions
   • D) To handle success cases only
2. What does Success represent in Scala’s Try?
   • A) An exception was thrown
   • B) A successful computation without errors
   • C) A default value
   • D) A failed operation
3. What does Failure represent in Scala’s Try?
   • A) A successful computation without errors
   • B) A failed operation with an exception
   • C) A successful result wrapped in a value
   • D) A non-terminating operation
4. Which of the following is used to handle Success in Scala?
   • A) .isSuccess
   • B) .get
   • C) .foreach
   • D) .map
5. What type of value does Failure hold in Scala?
   • A) An exception
   • B) A string message
   • C) A boolean flag
   • D) An integer
6. Which of the following is true about the Try class in Scala?
   • A) It wraps computations that can succeed or fail
   • B) It only handles exceptions that happen during execution
   • C) It only handles RuntimeException
   • D) It cannot be used with Success and Failure
7. What happens when Try is used to catch an exception in Scala?
   • A) The program terminates with a message
   • B) It returns Failure with the exception
   • C) It returns Success with the exception message
   • D) It ignores the exception and continues
8. Which method can be used to get the result from Try in Scala?
   • A) get
   • B) value
   • C) result
   • D) run
9. How would you handle a Try to extract the value without throwing an exception?
   • A) .recover
   • B) .getOrElse
   • C) .value
   • D) .map
10. What will the get method return when applied to a Failure?
    • A) The exception that caused the failure
    • B) A success value
    • C) Null
    • D) A new instance of the exception

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2. Catching Exceptions

11. What does the catch block in a try-catch expression in Scala do?
    • A) It specifies the exceptions to be caught
    • B) It always executes after the try block
    • C) It catches exceptions and prevents further execution
    • D) It defines the return type of the try block
12. Which of the following exceptions can be caught in Scala?
    • A) Only checked exceptions
    • B) Only unchecked exceptions
    • C) Both checked and unchecked exceptions
    • D) None of the above
13. How do you catch multiple exceptions in a try-catch block in Scala?
    • A) Using multiple catch blocks
    • B) By using a single catch block with multiple exception types
    • C) By using a catchAll block
    • D) By chaining catch statements
14. What is the base class for all exceptions in Scala?
    • A) Exception
    • B) Throwable
    • C) Error
    • D) RuntimeException
15. How can you catch an exception and log its details in Scala?
    • A) Use printStackTrace() inside the catch block
    • B) Use println() to output the exception message
    • C) Both A and B
    • D) You cannot log exceptions in Scala
16. Which of these statements will rethrow an exception after it is caught?
    • A) throw ex
    • B) return ex
    • C) ex.retry()
    • D) ex.finish()
17. What does the finally block in Scala’s try-catch-finally do?
    • A) It executes only when no exceptions are thrown
    • B) It runs after the try and catch blocks regardless of an exception
    • C) It is optional and can be removed
    • D) It executes before try
18. What will happen if an exception is caught but not rethrown in a catch block?
    • A) The program will stop executing
    • B) The exception will be logged only
    • C) The program continues executing normally
    • D) The program will terminate
19. Which of the following statements is true about checked exceptions in Scala?
    • A) They must be caught or declared in the method signature
    • B) They are ignored by default
    • C) Scala does not have checked exceptions
    • D) They are never thrown in Scala
20. In Scala, how can you specify the type of exception to catch in a catch block?
    • A) By using the catchType method
    • B) By providing the exception type directly after case
    • C) By using catchAll keyword
    • D) It is not possible to specify a specific exception

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3. Debugging Basics

21. What is the purpose of debugging in Scala?
    • A) To find and fix syntax errors
    • B) To identify and resolve runtime issues
    • C) To optimize performance
    • D) To improve the speed of compilation
22. What is a breakpoint in Scala debugging?
    • A) A line of code where execution is paused
    • B) A marker indicating an error
    • C) A place where the program starts
    • D) A function call
23. How do you inspect the value of variables while debugging in Scala?
    • A) By using println() statements
    • B) By setting breakpoints and examining variable values in the debugger
    • C) By using catch statements
    • D) By printing out the stack trace
24. Which Scala feature can help you to log messages for debugging?
    • A) println()
    • B) Logger class
    • C) trace() method
    • D) assert()
25. What is a stack trace used for in debugging?
    • A) To display a list of function calls leading to the error
    • B) To show the exception message only
    • C) To list the memory usage of the program
    • D) To list the global variables in use
26. Which of the following is an essential tool for debugging in Scala?
    • A) Stack trace
    • B) Profilers
    • C) Debugger
    • D) All of the above
27. What does stepping over a line of code in the debugger mean?
    • A) The debugger moves to the next line in the current method
    • B) The debugger jumps to a different method
    • C) The debugger executes the code but doesn’t step into method calls
    • D) The debugger skips over the current function entirely
28. How can you prevent certain parts of your code from being executed during debugging?
    • A) By using assert() statements
    • B) By using conditional breakpoints
    • C) By using try-catch blocks
    • D) By commenting out the code
29. What is a watch expression used for in Scala debugging?
    • A) To pause execution based on variable values
    • B) To execute a function only when an exception occurs
    • C) To log all variable changes during execution
    • D) To display variable values at every breakpoint
30. How can you debug a Scala program in IntelliJ IDEA?
    • A) By setting breakpoints and running the program in debug mode
    • B) By using the println() function
    • C) By inspecting the code manually
    • D) Debugging is not possible in IntelliJ IDEA

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Answers

Qno	Answer
1	B) To execute code in a safe way that can return a success or failure
2	B) A successful computation without errors
3	B) A failed operation with an exception
4	C) .foreach
5	A) An exception
6	A) It wraps computations that can succeed or fail
7	B) It returns Failure with the exception
8	A) get
9	B) .getOrElse
10	A) The exception that caused the failure
11	A) It specifies the exceptions to be caught
12	C) Both checked and unchecked exceptions
13	B) By using a single catch block with multiple exception types
14	B) Throwable
15	C) Both A and B
16	A) throw ex
17	B) It runs after the try and catch blocks regardless of an exception
18	C) The program continues executing normally
19	C) Scala does not have checked exceptions
20	B) By providing the exception type directly after case
21	B) To identify and resolve runtime issues
22	A) A line of code where execution is paused
23	B) By setting breakpoints and examining variable values in the debugger
24	B) Logger class
25	A) To display a list of function calls leading to the error
26	D) All of the above
27	C) The debugger executes the code but doesn’t step into method calls
28	B) By using conditional breakpoints
29	A) To pause execution based on variable values
30	A) By setting breakpoints and running the program in debug mode