Question 1

Complete the code shown to define the Comparator interface for comparing Auto objects. A)public class Comparator B)public class Comparator implements Comparator C)public interface Comparator D)public interface Auto

Accepted Answer

The correct syntax for defining a Comparator interface is "public interface Comparator" where T is the type of objects being compared. Therefore, the correct code to define the Comparator interface for comparing Auto objects is "public interface Comparator".

Question 2

Which of the following statements correctly provides a comparator function using lambda expressions to sort an array of countries by population, assuming the existence of a getPopulation method?
A)Arrays.sort(countries, comparator(c -> c.getPopulation()));
B)Arrays.sort(countries, compare(c1 -> c1.getPopulation(), c2 -> c2.getPopulation());
C)Arrays.sort(countries, (c1, c2) -> c1.getPopulation() - c2.getPopulation());
D)Arrays.sort(countries, c -> c.getPopulation());

Accepted Answer

Option C correctly provides a comparator function using lambda expressions to sort an array of countries by population. It subtracts the population of the second element from the first element, which gives a negative value if the first element's population is smaller than that of the second element, and the opposite if the first element's population greater than the second element one. This results into sorting the array in ascending order by population.

Question 3

What must be true about the return value from the implementation of the compare method for the Comparator interface when comparing two objects, a and b with a call to compare(a, b)?
A)It must return 1 if a comes before b, 0 if they are the same, and -1 if a comes after b.
B)It must return a negative value if a comes before b, 0 if they are the same, and a positive value if a comes after b.
C)It must return a positive value if a comes before b, 0 if they are the same, and a negative value if a comes after b.
D)It must return -1 if a comes before b, 0 if they are the same, and 1 if a comes after b.

Accepted Answer

According to the documentation of the Comparator interface, the compare method must return a negative integer, zero, or a positive integer as the first argument is less than, equal to, or greater than the second. Therefore, option B is the correct choice.

Question 4

Suppose a developer gets class XYZ files and documentation from a subcontractor.This class does not implement the Comparable interface.What must be true in order for the developer to sort an array of XYZ objects without modifying the XYZ class?
A)The XYZ class must implement the Sortable interface.
B)XYZ objects must be randomly distributed.
C)XYZ objects must be ordered.
D)The developer must supply a comparator object belonging to a class that implements the Comparator<XYZ> interface.

Accepted Answer

In order to sort an array of XYZ objects without modifying the XYZ class, the developer must supply a comparator object belonging to a class that implements the Comparator<XYZ> interface. This allows the developer to define the logic for how the objects should be sorted without needing to modify the original class.

Question 5

Which of the following classes implement the Comparable interface?
i.Date
II.Collections
III.String
A)I only
B)I and III only
C)I and II only
D)II and III only

Accepted Answer

Only the Date and String classes implement the Comparable interface, which is used to compare and sort objects of the same class. Collections is a class that provides static methods for working with collections such as sorting and searching, but it does not implement the Comparable interface directly.

Question 6

The ____ class contains a sort method that can sort array lists.
A)Sorting
B)Linear
C)Collections
D)Arrays

Accepted Answer

The Collections class in Java contains a sort method that can sort array lists. The Sorting class, Linear class, and Arrays class do not have this method.

Question 7

Suppose the call obj1.compareTo(obj2) returns 0.What can definitely be concluded from the return value?
i.obj1 and obj2 are the same object
II.obj1 and obj2 objects cannot be compared
III.the properties of obj1 and obj2 that are being compared have equal values
A)II only
B)III only
C)I only
D)I and III only

Accepted Answer

III is correct because a return value of 0 from compareTo() indicates that the objects are considered equal in terms of the ordering. This does not necessarily mean they are the same object (I is incorrect), nor does it indicate that they cannot be compared (II is incorrect), as the comparison has already been successfully made.

Question 8

Which of the following statements correctly specifies the use of lambda expressions and the comparing method of the Comparator functional interface to sort an array of countries by population, assuming the existence of a getPopulation method?
A)Arrays.sort(countries, Comparator.comparing(c1 -> c1.getPopulation(), c2 -> c2.getPopulation());
B)Arrays.sort(countries, comparing(c -> c.getPopulation()));
C)Arrays.sort(countries, c -> c.getPopulation());
D)Arrays.sort(countries, Comparator.comparing(c -> c.getPopulation());

Accepted Answer

The answer of Which of the following statements correctly specifies...

Question 9

The binarySearch method of the Collections class returns a value in the form of -k - 1 when the target item you are searching for was not found in the array.What does k represent?
A)It represents the index at which the target item should be inserted.
B)It represents the number of times the array was accessed by the binarySearch method, and can be used for analyzing performance.
C)Nothing - it is an arbitrary value.
D)It is the position of an existing item, and indicates that your target item should come after this existing item.

Accepted Answer

The value returned by binarySearch method is in the form of -k - 1, where k represents the index at which the target element should be inserted in the sorted array.

Question 10

Suppose you wish to implement the Comparable interface to allow your Vehicle class to compare Auto objects only.Which of the following is the correct way to do this? A)public class Auto implements Comparable B)public class Vehicle implements Comparable(Auto) C)public class Vehicle implements Comparable D)public class Vehicle implements Comparable

Accepted Answer

Since we want the Vehicle class to compare Auto objects only, we should implement the Comparable interface with the Auto class as the generic parameter. Therefore, option D is the correct answer. Option A is incorrect because it suggests implementing Comparable with the Vehicle class as the generic parameter, which is not what we want. Option B is incorrect because it uses parentheses instead of angle brackets when specifying the generic parameter. Option C is incorrect because it does not specify a generic parameter for the Comparable interface.

Question 11

If a call to the Arrays static method binarySearch returns a value of 7, what can be concluded?
i.the element is not in the array
II.the element is at index 7
III.the element occurs 7 times in the array
A)II and III only
B)I only
C)II only
D)III only

Accepted Answer

If the binarySearch method returns a value of 7, it means that the element is at index 7 in the sorted array. Therefore, only statement II is true. Statement I is not necessarily true, as the element could still be in the array at a different index. Statement III is not relevant, as the binarySearch method does not return information about the number of occurrences of an element in the array.

Question 12

Suppose you wish to sort an array list of objects, but the object class does not implement the Comparable interface.Because you are not allowed to modify this class, you decide to provide a comparator object that implements the Comparator interface.Which method must you implement from this interface to achieve your objective?
A)sort
B)compareObject
C)compare
D)compareTo

Accepted Answer

To achieve the objective of sorting an array list of objects where the object class does not implement the Comparable interface, we need to provide a comparator object that implements the Comparator interface. The Comparator interface has only one method that must be implemented, which is the compare() method. This method takes two objects as arguments and returns an integer value based on how the objects compare to each other. The compare() method is used to compare two objects during the sorting process. Therefore, option C is the correct answer.

Question 13

The Comparable interface consists of a single method called ____.
A)comparator
B)comparable
C)compare
D)compareTo

Accepted Answer

The Comparable interface consists of a single method called compareTo(), which compares the current object with the specified object for order. Therefore, the correct choice is D.

Question 14

Suppose objects a and b are from a user-defined class that implements the Comparable interface.What must be true about the return value of a.compareTo(b) for the compareTo method that this class implements?
A)It must return 1 if a comes before b, 0 if they are the same, and -1 if a comes after b.
B)It must return -1 if a comes before b, 0 if they are the same, and 1 if a comes after b.
C)It must return a negative value if a comes before b, 0 if they are the same, and a positive value if a comes after b.
D)It must return a positive value if a comes before b, 0 if they are the same, and a negative value if a comes after b.

Accepted Answer

According to the Java documentation, the compareTo method must return a negative value if the invoking object is less than the argument, zero if they are equal, and a positive value if the invoking object is greater than the argument. Therefore, option C is the correct choice.

Question 15

Given the following code snippet for searching an array:  What value will pos have when this code is executed? 
A)0
B)1
C)-2
D)-1

Accepted Answer

The value of 'pos' will be -1, which indicates that the string was not found in the array.

Question 16

Suppose objects a and b are from a user-defined class that implements the Comparable interface.Which condition tests the compareTo method's return value to determine that a will precede b when the sort method is called?
A)a.compareTo(b) == -1
B)a.compareTo(b) < 0
C)a.compareTo(b) == 0
D)a.compareTo(b) > 0

Accepted Answer

The compareTo method returns a negative integer if the calling object is less than the argument object, zero if they are equal, and a positive integer if the calling object is greater than the argument object. Therefore, to determine that a will precede b when the sort method is called, we need to test that the result of a.compareTo(b) is less than 0, which is equivalent to choice B.

Question 17

Given the following code snippet for searching an array:  What value will pos have when this code is executed? 
A)6
B)-5
C)-6
D)5

Accepted Answer

The answer of Given the following code snippet for searching...

Question 18

Which of the following arrays can be used in a call to the Arrays.sort method?
i.Any array with primitive numeric data, such as int, double, …
II.Arrays of String or numeric wrapper classes like, Integer, Double, …
III.Any class that implements the Comparable interface
A)I, II and III
B)II only
C)I only
D)I and II only

Accepted Answer

- Option I includes all primitive numeric data types which are sortable.
- Option II includes Strings and numeric wrapper classes which implement the Comparable interface and can therefore be sorted using Arrays.sort().
- Option III includes any class that implements the Comparable interface, making it sortable.

Question 19

Complete the code shown to define the Comparator interface for comparing Auto objects.  
A)boolean compare(Auto a, Auto b);
B)single compare(Auto a, Auto b);
C)single compareTo(Auto a, Auto b);
D)int compare(Auto a, Auto b);

Accepted Answer

The best choice for defining the Comparator interface for comparing Auto objects is option D because it uses the correct signature for the compare method in the Comparator interface, which takes two objects of the parameterized type and returns an integer value. The integer returned should be negative if the first object is smaller than the second, zero if they are equal, and positive if the first object is larger than the second.

Question 20

If a call to the Arrays static method binarySearch returns a value of -10, what can be concluded?
i.the element is not in the array
II.the element is at index 10
III.the element can be inserted at index 9
A)II only
B)I and III only
C)III only
D)I only

Accepted Answer

When the `binarySearch` method in Java returns a negative value, it means the element is not found in the array. The return value is `-(insertion point) - 1`. Therefore, if it returns -10, the insertion point is at index 9 (since -(-10) - 1 = 9), indicating both that the element is not in the array and it can be inserted at index 9 to maintain sorted order.

Quiz 14: Sorting and Searching

Complete the code shown to define the Comparator interface for comparing Auto objects.

Which of the following statements correctly provides a comparator function using lambda expressions to sort an array of countries by population, assuming the existence of a getPopulation method?

What must be true about the return value from the implementation of the compare method for the Comparator interface when comparing two objects, a and b with a call to compare(a, b) ?

Suppose a developer gets class XYZ files and documentation from a subcontractor.This class does not implement the Comparable interface.What must be true in order for the developer to sort an array of XYZ objects without modifying the XYZ class?

Which of the following classes implement the Comparable interface? i.Date II.Collections III.String

The ____ class contains a sort method that can sort array lists.

Suppose the call obj1.compareTo(obj2) returns 0.What can definitely be concluded from the return value? i.obj1 and obj2 are the same object II.obj1 and obj2 objects cannot be compared III.the properties of obj1 and obj2 that are being compared have equal values

Which of the following statements correctly specifies the use of lambda expressions and the comparing method of the Comparator functional interface to sort an array of countries by population, assuming the existence of a getPopulation method?

The binarySearch method of the Collections class returns a value in the form of -k - 1 when the target item you are searching for was not found in the array.What does k represent?

Suppose you wish to implement the Comparable interface to allow your Vehicle class to compare Auto objects only.Which of the following is the correct way to do this?

If a call to the Arrays static method binarySearch returns a value of 7, what can be concluded? i.the element is not in the array II.the element is at index 7 III.the element occurs 7 times in the array

The Comparable interface consists of a single method called ____.

Suppose objects a and b are from a user-defined class that implements the Comparable interface.What must be true about the return value of a.compareTo(b) for the compareTo method that this class implements?

Given the following code snippet for searching an array: What value will pos have when this code is executed?

Suppose objects a and b are from a user-defined class that implements the Comparable interface.Which condition tests the compareTo method's return value to determine that a will precede b when the sort method is called?

Given the following code snippet for searching an array: What value will pos have when this code is executed?

Which of the following arrays can be used in a call to the Arrays.sort method? i.Any array with primitive numeric data, such as int, double, … II.Arrays of String or numeric wrapper classes like, Integer, Double, … III.Any class that implements the Comparable interface

Complete the code shown to define the Comparator interface for comparing Auto objects.

If a call to the Arrays static method binarySearch returns a value of -10, what can be concluded? i.the element is not in the array II.the element is at index 10 III.the element can be inserted at index 9