Questions and Answers
- Scala bytecode can run on top of Java VM. What is the fundamental difference between Java object.clone() and Scala object.copy()?
- One is a Java object, the other is a Scala object.
- clone() will copy class structures but not the data, while copy() will also copy data into new objects.
- There is no difference.
- copy() allows you to change values during the copying process; clone() does not.
- What value does this code return?
- a
- 2
- b
- 1
- What is one way to avoid low-level parallelization details?
- monads
- literal functions
- partially applied functions
- parallel collections
- What do you use in ScalaTest to see a detailed diagram of error messages when a test fails?
- ArgumentExceptions
- AssertionException
- DiagrammedAssertions
- JUnit
- What data type would you use to store an immutable collection of objects that contain a fixed number of varying types?
- Array
- ImmutableCollection
- List
- Tuple
- After defining a function in the interpreter, Scala returns the following. What does the `()` indicate?
- The function has no side effects.
- The function takes no parameters.
- The function returns no value.
- Returning unit types to the function is a closures.
- What type of number is 1234.e5?
- hexadecimal
- short
- floating point
- long
- When you convert a map to a list using the `toList` method of the map, the result will be of which type?
- `List[(String, String)]`
- `List[(Array, Array)]`
- `List[(Collection, Collection)]`
- `List`
- What type of object does this code create?
- List
- Map
- Tuple
- Array
- Which is a subclass of all classes?
- AnyVal
- AnyRef
- Method
- Null
- For the for-yield construct, is the scope separate between for-body and yield-body?
- Yes and no. It is different depending on the for construct and what it does.
- Yes, because the for section does not expose its scope.
- No, because for-yield shares the same scope, even though they are within separate curly braces.
- Yes, because they are within different curly braces.
- What is one way to implement pattern matching on methods?
- using regex
- using monads
- using string matching
- using case classes
- What is the value of z after executing this code?
- List(a,b,c)
- List(List(a, b), c)
- List(c,a,b)
- List(c,List(a,b))
- What term is used to specify a precondition?
- assert
- require
- precondition
- mustHave
- Which Scala type may throw an exception or a successfully computed value, and is commonly used to trap and propagate errors?
- `scala.util.ExceptionHandling`
- `scala.Catch.Throw`
- `scala.exception.TryFinally`
- `scala.util.Try`
- What is the data type of y after this code is executed?
- short
- double
- int
- bigInt
- When using pattern matching, which character matches on any object?
- `%`
- `_`
- `^`
- `-`
- You have created an array using val. Can you change the value of any element of the array?and why or why not?
- Yes, the reference to the array is immutable, so the location that the array points to is immutable. The values in the array are mutable.
- The 0th element is immutable and cannot be modified. All other elements can be modified.
- Yes, val does not make arrays immutable.
- No, val makes the array and values of the array immutable.
- What is the output of this function?
- 1,2,3,4,5
- 0,1,2,3,4
- 1,2,3,4
- 2,3,4,5
- What do you call objects with immutable state?
- singletons
- stationary objects
- functional objects
- fixed objects
- You have written a Scala script. How would you access command-line arguments in the script?
- use array named args
- use tuple named args
- use numbered variables with a _ prefix for example _ 1, _ 2, _ 3
- use numbered variables with a $ prefix - for example $1, $2, $3
- What does this code return? `val x = 3; if (x > 2) x = 4 else x = x*2`
- 4
- an error
- 6
- 3
- Which statement returns a success or a failure indicator when you execute this code?
- myFuture.onComplete
- myFuture(status)
- myFuture.Finished
- complete(myFuture)
- To denote a parameter that may be repeated, what should you place after type?
- `%`
- `&`
- `_`
- `-`
- What is called when a superclass has more than one subclass in Scala?
- polyinheritance
- multilevel inheritance
- multimode inheritance
- hierarchical inheritance
- One way to improve code reliability is to use `__` , which will evaluate a condition and return an error if the condition is violated.
- packages
- polymorphisms
- assertions
- traits
- Which statement about if-else-if-else statements is true?
- If the first else-if does not succeed, then no other else-ifs are tested.
- If an else-if does not succeed, then none of the remaining else-if statements or elses will be tested.
- All else-if statements are tested in all cases.
- If an else-if succeeds, then none of the remaining else-if statements or elses will tested.
- What do you call the process of changing the definition of an inherited method?
- recursive methods
- currying methods
- redefining methods
- overriding methods
- To denote a parameter that may be repeated, what should you place after the type?
- `_`
- `*`
- `%`
- `&`
- What is the code below equivalent to?
- `myClass.foreach(println ())`
- `myClass.foreach(print NIL)`
- `myClass.loop(println ())`
- `myClass.foreach(x => println(x))`
- What is an advantage of an immutable object?
- Immutable objects use less memory than their mutable counterparts.
- Immutable objects do not require error handling.
- Immutable objects can be used in classes, mutable objects cannot.
- Immutable objects are threadsafe.
- You want to create an iteration loop that tests the condition at the end of the loop body. Which iteration would you use?
- do-while loop
- while loop
- for loop
- do-until loop
- What can you use to make querying a database more efficient, by avoiding the need to parse the SQL string every time a query is executed from Scala?
- database driver
- connection
- prepared statement
- SQL view
- Which is _not_ a member of the collections hierarchy?
- Set
- Seq
- Hash
- Map
- Which term makes the contents of packages available without prefixing?
- use
- include
- import
- assertion
- If you wanted to find the remainder after division, what operator would you use?
- %
- DIV
- //
- /
- What are defined inside a class definition?
- method
- fields and methods
- fields, methods, and packages
- fields
- What defines methods and fields that can then be reused by mixing into classes?
- singleton
- assertion
- trait
- monad
- When do you need to explicitly state the return type in a function definition?
- when the function has no side effects
- when the function returns a Unit type
- when the function is recursive
- when the function has side effects
- Why would you make a field private?
- so only methods in the same file can access the field
- so only methods in the same package can access the field
- so only methods in the same class could access the field
- so only methods defined in a Java class can access the field
- What's the difference between `.equals` and `==`?
- They do the exact same thing
- `==` won't work on objects
- `==` cannot be applied to `String`
- `==` is a wrapper of `.equals()` and checks for nulls
- What is denotes the intersection between two sets?
- ||
- &&
- &
- %
- What do you call a function defined in a block?
- private function
- block function
- local function
- method
- What do you call a Scala method that is parametrized by type as well as by value?
- multimode method
- polymorphic method
- closure
- collection method
- What type of exception is thrown when a precondition is violated?
- IllegalArgumentException
- NumberFormatException
- NullPointerExcepetion
- MalformedParameterException
- In scala what is precondition?
- a constraint on where a method may be called from
- a constraint on values passed to a methode constructor
- a class of predifined error messages
- a class of Boolean operators
- What would you change in this code to make it execute in parallel?
- Change **list.map** to **list.par.map.**
- Change **toList** to **toListPar**
- Change **val** to **val.par**
- Change **toList** to **toParallelList**
- What is a free variable?
- a variable defined outside a function
- a variable referenced in a function that is not assigned a value by that function
- a variable that has a global scope
- a variable defined in a class and available to all methods in that class
- What's the best way to execute code in the background in a separate thread?
- AltThread
- AltFuture
- AltProcess
- Future
- What value does this code return?
- (1,2,4)
- 1
- Nil
- 2