Question 1

A __________ operation triggers the lazy operations on a stream and yields a non-stream value.

Accepted Answer

Terminal operations are those that trigger the processing of a stream and return a result or a side effect. They are called terminal because the stream cannot be used anymore after a terminal operation has been performed on it. Non-terminal operations, also called intermediate operations, return a stream so that multiple operations can be chained together. While parallel and distributed operations are possible on streams, they are not relevant to this specific question.

Question 2

Which lambda expression represents a function that computes a 10% raise to an employee's salary?

Accepted Answer

To compute a 10% raise to an employee's salary, we need to add 10% of the current salary to the current salary. So, the lambda expression that represents this function is s -> s + .10 * s or s -> 1.1 * s. Option D represents this lambda expression.

Question 3

Complete the following code snippet that displays a student's major, assuming that the method findStudentByID takes a student id as input and returns a result of type Optional.Also, assume the getMajor method returns a String representing the student's major. Optional studentSearch = findStudentByID("123456789"); if (____________________) { System.out.println(studentSearch.get().getMajor()); } else { System.out.println("Student does not exist"); }

Accepted Answer

Since the findStudentByID method returns an Optional object, we should check if that object contains a value using the isPresent() method before calling any methods like get(). This is because calling get() on an Optional object that contains no value will result in a NoSuchElementException. Therefore, the correct choice is C.

Question 4

The method reference System.out::println is a shorthand for which expression?

Accepted Answer

The method reference System.out::println is equivalent to the lambda expression n -> System.out.println(n), where 'n' is the parameter passed to the println method.

Question 5

Complete the code to sort the employees collection by salary using a Comparator.Assume the method getSalary that returns an employee's salary as an integer.
Collections.sort(employees, _____________________________________);

Accepted Answer

The correct syntax to sort the employees collection by salary using a Comparator is Comparator.comparing(Employee::getSalary). This method reference compares the salaries of two employees and returns the result of the comparison. It is used directly as the argument of Collections.sort() method.

Question 6

Complete the following code snippet that returns the name of an employee who is a Database Administrator or "None" if there are no such titled employees.

Accepted Answer

The answer of Complete the following code snippet that returns...

Question 7

What does the following lambda expression do, assuming the variable p is of type double and the variable q is of type int?
(p, q) -> p * q

Accepted Answer

The lambda expression takes two parameters p and q and multiplies them, so the result is the value of p multiplied by q.

Question 8

The constructor reference Student[]::new is a shorthand for which expression?

Accepted Answer

The constructor reference Student[]::new refers to a constructor for an array of Students. The shorthand for this is n -> new Student[n], where n represents the size of the array. Therefore, the correct answer is B.

Question 9

Which statement about higher-order functions is NOT correct?

Accepted Answer

This statement is not correct as a higher-order function can return a function. Examples of such functions include currying functions or functions that generate other functions based on the input.

Question 10

Complete the following code snippet that checks a log for any error message and sends an alert with the message found using the alert method.

Accepted Answer

The answer of Complete the following code snippet that checks...

Question 11

Consider the following pseudocode that returns an Optional value from a method:
if there is a result // line 1
return the result // line 2
else
return an empty result // line 3
Assume that the variable result represents an object reference to the result to be returned as Optional.Replace line 3 with the Java code to return an empty result.

Accepted Answer

Option A correctly returns an empty optional using the static method Optional.empty(). Option B is not valid syntax for creating an empty optional, as Optional.empty() takes no arguments. Option C is not a valid way to create an empty optional, as it implies that the object reference itself has an empty method, rather than the Optional class. Option D returns null, which is not an Optional value.

Question 12

Which of the following statements related to the Optional type is NOT correct?

Accepted Answer

The Optional.of method creates a single Optional object containing the provided value as its content, not a stream of Optional objects.

Question 13

Which of the following is NOT a method for the Optional class?

Accepted Answer

The correct method names for the Optional class in Java include empty(), of(), and orElse(), but present() is not a method of the Optional class.

Question 14

Consider the following pseudocode that returns an Optional value from a method:
if there is a result // line 1
return the result // line 2
else
return an empty result // line 3
Assume that the variable result represents an object reference to the result to be returned as Optional.Replace line 2 with the Java code to return the result.

Accepted Answer

When returning a value as Optional, we use the Optional.of() method to wrap the return value. Therefore, D is the correct option.

Question 15

Which Java interface is NOT a functional interface?

Accepted Answer

Collection is not a functional interface because it has multiple abstract methods, including add(), remove(), and contains(). A functional interface can only have one abstract method. The other options, Predicate, Comparator, and ActionListener, are all functional interfaces.

Question 16

Which of the following statements does NOT return a value of type Optional, assuming that the variable result is of type Optional<String>?

Accepted Answer

Option A does not return a value of type Optional because the `orElse` method returns a non-optional result, specifically the contained value if present, or the argument ("None" in this case) if not.

Question 17

Complete the code to sort the employees collection by title and within title by salary using a Comparator.Assume the method getSalary that returns an employee's salary as an integer and the method getTitle that returns an employee's title as a String.
Collections.sort(employees, Comparator___________________________);

Accepted Answer

We should first sort by title using `comparing(Employee::getTitle)` and then within each title group, we should sort by salary using `thenComparing(Employee::getSalary)`.

Question 18

Which lambda expression represents a function that given the price and quantity of an item to purchase computes the cost of the quantity of that item on the invoice?

Accepted Answer

The lambda expression (p, q) -> p * q takes in the price and quantity of an item and returns the cost of the quantity of that item on the invoice by multiplying them.

Question 19

Complete the following code snippet, assuming that method findEmployeeByID takes an employee id as input and returns a result of type Optional and method displayEmployee takes an Employee object as input and displays the employee's information. Optional empSearch = findEmployeeByID("123456789"); if (empSearch.isPresent()) { _____________________________ } else { System.out.println("Employee does not exist"); }

Accepted Answer

Since empSearch is of type Optional<Employee>, we need to use the get() method to retrieve the Employee object inside the Optional. Then we can pass that Employee object as argument to the displayEmployee method. However, we need to make sure that empSearch.isPresent() is true before calling get(), to prevent a NoSuchElementException. Therefore, option B is the correct choice.

Question 20

Consider the following pseudocode that returns an Optional value from a method:
if there is a result // line 1
return the result // line 2
else
return an empty result // line 3
Assume that the variable result represents an object reference to the result to be returned as Optional.Replace line 1 with the Java code to determine whether there is a result.

Accepted Answer

The correct Java code to determine whether there is a result (i.e., the result is not null) before wrapping it in an Optional is `if (result != null)`. This checks if the `result` variable holds a reference to an object, indicating that there is a result to return.

Quiz 19: Stream Processing