Deck 17: Lambdas

Question 1

The type of a lambda is the type of the ________ that the lambda implements.

A) anonymous class
B) functional interface
C) stream
D) collection

Answer 1

B

Question 2

The intermediate Stream operation ________ results in a stream containing only the unique elements.

A) distinct
B) map
C) filter
D) limit

Answer 2

A

Question 3

The basic generic functional interface ________ in package java.util.function contains method test that takes a T argument and returns a boolean. Tests whether the T argument satisfies a condition.

A) Consumer
B) Function
C) Supplier
D) Predicate

Answer 3

D

Question 4

Prior to Java SE 8, Java supported three programming paradigms. Java SE 8 adds ________.

A) procedural programming
B) object-oriented programming
C) generic programming
D) functional programming.

Question 5

Which of the following statements is false?

A) A lambda that receives two ints, x and y, and returns their sum is (int x, int y) -> {return x + y;}
B) A lambda's parameter types may be omitted, as in: (x, y) -> {return x + y;}
In which case, the parameter and return types are set to the lambda's default type.
C) A lambda with a one-expression body can be written as: (x, y) -> x + y
In this case, the expression's value is implicitly returned.
D) When a lambda's parameter list contains only one parameter, the parentheses may be omitted, as in: value -> System.out.printf("%d ", value)

Question 6

Which of the following statements is false?

A) Lambda expressions can be used anywhere functional interfaces are expected.
B) A lambda consists of a parameter list followed by the arrow token and a body, as in: [parameterList] -> {statements}
C)Method references are specialized shorthand forms of lambdas.
D) Each of the above statements is true.

Question 7

The basic generic functional interface ________ in package java.util.function contains method apply that takes a T argument and returns a value of type R. Calls a method on the T argument and returns that method's result.

A) Consumer
B) Function
C) Supplier
D) BinaryOperator

Question 8

Which of the following statements is false?

A) Prior to functional programming, you typically determined what you wanted to accomplish, then specified the precise steps to accomplish that task.
B) Using a loop to iterate over a collection of elements is known as external iteration and requires accessing the elements sequentially. Such iteration also requires mutable variables. External iteration is easier to parallelize.
C) Letting the library determine how to iterate over a collection of elements is known as internal iteration.
D) Functional programming focuses on immutability-not modifying the data source being processed or any other program state.

Question 9

The basic generic functional interface ________ in package java.util.function contains method get that takes no arguments and returns a value of type T.

A) UnaryOperator
B) Function
C) Supplier
D) BinaryOperator

Question 10

Intermediate Stream operation ________ results in a stream with the specified number of elements from the beginning of the original stream.

A) distinct
B) map
C) filter
D) limit

Question 11

Intermediate Stream operation ________ results in a stream in which each element of the original stream is mapped to a new value (possibly of a different type)-e.g., mapping numeric values to the squares of the numeric values. The new stream has the same number of elements as the original stream.

A) mapped
B) map
C) mapper
D) mapping

Question 12

Intermediate operations are________; they aren't performed until a terminal operation is invoked. This allows library developers to optimize stream-processing performance.

A) eager
B) idle
C) lazy
D) inactive

Question 13

The basic generic functional interface ________ in package java.util.function contains method get that takes no arguments and produces a value of type T. Often used to create a collection object in which a stream operation's results are placed.

A) Consumer
B) Function
C) Supplier
D) BinaryOperator

Question 14

The intermediate Stream operation ________ results in a stream containing only the elements that satisfy a condition.

A) distinct
B) map
C) filter
D) limit

Question 15

What is the meaning of ( ) in the following lambda?
() -> System.out.println("Welcome to lambdas!")

A) the lambdas parameters are inferred
B) the lambdas parameters are supplied by a method reference
C) the lambda has an empty parameter list
D) the given expression is not a valid lambda

Question 16

A lambda expression represents a(n) ________ method-a shorthand notation for implementing a functional interface.

A) functional
B) unnamed
C) undesignated
D) anonymous

Question 17

The basic generic functional interface ________ in package java.util.function contains method accept that takes a T argument and returns void. Performs a task with its T argument, such as outputting the object, invoking a method of the object, etc.

A) Consumer
B) Function
C) Supplier
D) BinaryOperator

Question 18

2.3 Q3:Terminal operations are eager; they perform the requested operation when they are called.

A) immediate
B) idle
C) lazy
D) eager

Question 19

The new language and library capabilities that support functional programming were added to Java as part of Project ________.

A) Utilitarian
B) Upsilon
C) Lambda
D) Utility

Question 20

The basic generic functional interface ________ in package java.util.function contains method apply that takes two T arguments, performs an operation on them (such as a calculation) and returns a value of type T.

A) Consumer
B) Function
C) Supplier
D) BinaryOperator

Question 21

Which of the following statements is false?

A) Stream method map maps each element to a new value and produces a new stream with the same number of elements as the original stream.
B) A reference is a shorthand notation for a lambda expression.
C) ClassName::instanceMethodName represents a method reference for an instance method of a class. Creates a one-parameter lambda that invokes the instance method on the lambda's argument and returns the method's result.
D) ClassName::new represents a constructor reference. Creates a lambda that invokes the no-argument constructor of the specified class to create and initialize a new object of that class.

Question 22

An ________ (package java.util.stream) is a specialized stream for manipulating int values.

A) StreamOfInt
B) IStream.
C) IntegerStream
D) IntStream

Question 23

Stream mutable reduction operation ________ creates a new collection of elements containing the results of the stream's prior operations.

A) combine
B) accumulate
C) gather
D) collect

Question 24

Method reduce's first argument is formally called a(n) ________ value-a value that, when combined with any stream element using the IntBinaryOperator produces that element's original value.

A) original
B) identity
C) preserve
D) self

Question 25

Which of the following statements is false?

A) You filter elements to produce a stream of intermediate results that match a predicate.
B) IntStream method filter receives an object that implements the IntPredicate functional interface (package java.util.function).
C) IntStream method sorted (a lazy operation) orders the elements of the stream into ascending order by default. All prior intermediate operations in the stream pipeline must be complete so that method sorted knows which elements to sort.
D) Method filter is a stateless intermediate operation-it requires information about other elements in the stream in order to test whether the current element satisfies the predicate.

Question 26

Class Array's ________ method is used to create a Stream from an array of objects.

A) stream
B) arrayToStream
C) createStream
D) objectToStream

Question 27

Terminal Stream operation ________ performs processing on every element in a stream (e.g., display each element).

A) forNext
B) for
C) forAll
D) forEach

Question 28

Which of the following statements is false?

A) Interface IntPredicate's default method and performs a logical AND operation with short-circuit evaluation between the IntPredicate on which it's called and its IntPredicate argument.
B) Interface IntPredicate's default method invert reverses the boolean value of the IntPredicate on which it's called.
C) Interface IntPredicate default method or performs a logical OR operation with short-circuit evaluation between the IntPredicate on which it's called and its IntPredicate argument.
D) You can use the interface IntPredicate default methods to compose more complex conditions.

Question 29

Stream reduction operation ________ uses the elements of a collection to produce a single value using an associative accumulation function (e.g., a lambda that adds two elements).

A) reduce
B) condense
C) combine
D) associate

Question 30

Which of the following statements is false?

A) IntStream methods range and rangeClosed each produce an ordered sequence of int values.
B) IntStream methods range and rangeClosed take two int arguments representing the range of values.
C) Method range produces a sequence of values from its first argument up to its second argument.
D) Method rangeClosed produces a sequence of values including both of its arguments.

Question 31

IntStream method ________performs the count, min, max, sum and average operations in one pass of an IntStream's elements and returns the results as an IntSummaryStatistics object (package java.util).

A) allStatistics.
B) completeStatistics.
C) entireStatistics.
D) summaryStatistics

Question 32

Which of the following statements is false?

A) A lambda can use the outer class's this reference without qualifying it with the outer class's name.
B) The parameter names and variable names that you use in lambdas cannot be the same as any other local variables in the lambda's lexical scope; otherwise, a compilation error occurs.
C) Lambdas may use only final local variables.
D) A lambda that refers to a local variable in the enclosing lexical scope is known as a capturing lambda.

Question 33

Stream mutable reduction operation ________creates an array containing the results of the stream's prior operations.

A) array
B) createArray
C) toArray
D) reduceArray

Question 34

________ is an intermediate operation that transforms a stream's elements to new values and produces a stream containing the resulting (possibly different type) elements.

A) Transforming
B) Converting
C) Mapping
D) Translating

Question 35

Class IntStream provides terminal operations for common stream ________-count returns the number of elements, min returns the smallest int, max returns the largest int, sum returns the sum of all the ints and average returns an OptionalDouble (package java.util) containing the average of the ints as a value of type double.

A) consolidations
B) deductions
C) reductions
D) trims

Question 36

By default, method sorted uses ________.

A) ascending order
B) the natural order for the stream's element type
C) descending order
D) the order specified in a command-line argument

Question 37

Interface Stream (package java.util.stream) is a generic interface for performing stream operations on objects. The types of objects that are processed are determined by the Stream's ________.

A) root
B) origin
C) source
D) start

Question 38

You can define your own reductions for an IntStream by calling its ________ method. The first argument is a value that helps you begin the reduction operation and the second argument is an object that implements the IntBinaryOperator functional interface.

A) reduction.
B) lessen
C) trim
D) reduce

Question 39

Class Arrays provides ________ stream methods for creating IntStreams, LongStreams and DoubleStreams from int, long and double arrays or from ranges of elements in the arrays.

A) virtual
B) package
C) overridden
D) overloaded

Question 40

Which of the following statements is true?

A) Stream method filter receives a Predicate and results in a stream of objects that match the Predicate.
B) Predicate method test returns a boolean indicating whether the argument satisfies a condition.
C) Interface Predicate also has methods and, negate and or.
D) Each of these statements is true.

Question 41

Stream method findFirst is a short-circuiting terminal operation that processes the stream pipeline and terminates processing as soon as the first object from the stream pipeline is found. The method returns a(n) ________ containing the object that was found, if any.

A) Optional
B) Discretionary
C) Elective
D) Extra

Question 42

Map method entrySet returns a Set of Map.Entry objects containing the Map's ________.

A) values
B) keys
C) index
D) key-value pairs

Question 43

Which of the following statements is false?

A) Functional interfaces must contain only one method and that method must be abstract.
B) When a class implements an interface with default methods and does not override them, the class inherits the default methods' implementations. An interface's designer can now evolve an interface by adding new default and static methods without breaking existing code that implements the interface. C If one class inherits the same default method from two interfaces, the class must override that method; otherwise, the compiler will generate a compilation error.
D) You can create your own functional interfaces by ensuring that each contains only one abstract method and zero or more default or static methods.

Question 44

________ is s method reference for a static method of a class. It creates a one-parameter lambda in which the lambda's argument is passed to the specified a static method and the lambda returns the method's result.

A) Math::sqrt
B) System.out::println
C) TreeMap::new
D) String::toUpperCase

Question 45

Which statement in the following sequence of statements about sorting objects by two fields is false?

A) To sort objects by two fields, you create a Comparator that uses two Functions.
B) First you call Comparator method comparing to create a Comparator with the first Function.
C) On the Comparator for the first field, you call method comparing with the second Function.
D) The resulting Comparator compares objects using the first Function then, for objects that are equal, compares them by the second Function.

Question 46

Collectors static method groupingBy with one argument receives a Function that classifies objects in the stream-the values returned by this function are used as the keys in a Map. The corresponding values, by default, are ________ containing the stream elements in a given category.

A) Lists
B) Arrays
C) Strings
D) Collectors

Question 47

________ is a method reference for an instance method that should be called on a specific object. It creates a one-parameter lambda that invokes the instance method on the specified object-passing the lambda's argument to the instance method-and returns the method's result.

A) Math::sqrt
B) System.out::println
C) TreeMap::new
D) String::toUpperCase

Question 48

Functional interface Comparator's default method ________ reverses an existing Comparator's ordering.

A) invert
B) descending
C) reversed
D) downward

Question 49

Map method ________ performs an operation on each key-value pair.

A) for
B) forNext
C) forEach
D) forAll

Question 50

Which of the following statements is false?

A) SecureRandom method ints with two int arguments creates an IntStream for an infinite stream of random int values in the range starting with the first argument and up to, but not including, the second.
B) SecureRandom method ints with a long and two int arguments creates an IntStream with the specified number of random int values in the range starting with the first argument and up to, but not including, the second.
C) To convert an IntStream to a Stream call IntStream method toStream.
D) Function static method identity creates a Function that simply returns its argument.

Question 51

Which of the following statements is false?

A) Files method lines creates a String containing the lines of text from a file.
B) Stream method flatMap receives a Function that maps an object into a stream-e.g., a line of text into words.
C) Pattern method splitAsStream uses a regular expression to tokenize a String.
D) Collectors method groupingBy with three arguments receives a classifier, a Map factory and a downstream Collector.

Question 52

Which of the following statements is false?

A) Class SecureRandom's methods ints, longs and doubles (inherited from class Random) return IntStream, LongStream and DoubleStream, respectively, for streams of random numbers.
B) SecureRandom method ints with no arguments creates an IntStream for an infinite stream of random int values.
C) An infinite stream is a stream with an unknown number of elements-you use an intermediate operation to complete processing on an infinite stream.
D) SecureRandom method ints with a long argument creates an IntStream with the specified number of random int values.

Question 53

Collectors static method groupingBy with two arguments receives a Function that classifies the objects in the stream and another Collector (known as the ________ Collector).

A) stream
B) downstream
C) grouping stream
D) upsteam

Question 54

You can declare that an interface is a functional interface by preceding it with the @FunctionalInterface annotation. The compiler will then ensure that the interface contains ________; otherwise, it'll generate a compilation error.

A) no abstract methods
B) all abstract methods
C) only one abstract method
D) one or more abstract methods.

Question 55

A nice performance feature of lazy evaluation is the ability to perform________ evaluation, that is, to stop processing the stream pipeline as soon as the desired result is available.

A) premature
B) short circuit
C) terminal
D) intermediate

Question 56

Functional interface BiConsumer's accept method has two parameters. For Maps, the first represents the ________ and the second the corresponding ________.

A) key, variable
B) lambda, value
C) lambda, variable
D) key, value

Question 57

Collectors static method ________ returns a Collector that counts the number of objects in a given classification, rather than collecting them into a List.

A) counter
B) count
C) counting
D) enumerate

Question 58

Which of the following statements is false?

A) Some event-listener interfaces are functional interfaces.
B) For such interfaces as mentioned in (a), you can implement event handlers with lambdas.
C) For a simple event handler, a lambda significantly reduces the amount of code you need to write.
D) All of the above are true.

Question 59

________ is a method reference for an instance method of a class. It creates a one-parameter lambda that invokes the instance method on the lambda's argument and returns the method's result.

A) Math::sqrt
B) System.out::println
C) TreeMap::new
D) String::toUpperCase

Question 60

________ is a constructor reference. It creates a lambda that invokes the no-argument constructor of the specified class to create and initialize a new object of that class.

A) Math::sqrt
B) System.out::println
C) TreeMap::new
D) String::toUpperCase