Deck 15: The Java Collections Framework

Question 1

A linear search only requires ____ access.
A.sorted
B.arbitrary
C.sequential
D.random

Answer 1

sequential

Question 2

A queue is a collection that ____.
A.remembers the order of elements, and allows elements to be added and removed only at one end.
B.remembers the order of elements and allows elements to be inserted only at one end and removed only at the other end.
C.does not remember the order of elements but allows elements to be added in any position.
D.remembers the order of elements and allows elements to be inserted in any position.

Answer 2

remembers the order of elements and allows elements to be inserted only at one end and removed only at the other end.

Question 3

What is included in a linked list node?
I a reference to its neighboring nodes
II an array reference
III a data element
A.II only
B.I and III only
C.I only
D.II and III only

Answer 3

I and III only

Question 4

Which of the following algorithms would be efficiently executed using a LinkedList?
A.Remove first n/ 2 elements from a list of n elements.
B.Read n / 2 elements in random order from a list of n elements.
C.Tracking paths in a maze.
D.Binary search.

Question 5

A collection that allows speedy insertion and removal of already-located elements in the middle of it is called a ____.
A.linked list
B.stack
C.set
D.queue

Question 6

The ArrayList class implements the ____ interface.
A.Stack
B.Queue
C.List
D.Set

Question 7

A stack is a collection that ____.
A.does not remember the order of elements but allows elements to be added in any position.
B.remembers the order of elements, and allows elements to be added and removed only at one end.
C.remembers the order of elements and allows elements to be inserted only at one end and removed only at the other end.
D.remembers the order of elements and allows elements to be inserted in any position.

Question 8

Which of the following statements about linked lists is correct?
A.When a node is removed, all nodes after the removed node must be moved down.
B.Visiting the elements of a linked list in random order is efficient.
C.Linked lists should be used when you know the correct position and need to insert and remove elements efficiently.
D.Even if you have located the correct position, adding elements in the middle of a linked list is inefficient.

Question 9

Which nodes need to be updated when we insert a new node to become the fourth node from the beginning of a doubly-linked list?
A.The current third and fourth nodes.
B.The current fourth and fifth nodes.
C.The current first node.
D.The current third node.

Question 10

Which data structure would best be used for keeping track of groceries to be purchased at the food market?
A.stack
B.queue
C.list
D.array

Question 11

We might choose to use a linked list over an array list when we will not require frequent ____.
I random access
II inserting new elements
III removing of elements
A.III only
B.II only
C.II and III only
D.I only

Question 12

Rather than storing values in an array, a linked list uses a sequence of ____.
A.accessors
B.nodes
C.elements
D.indexes

Question 13

A list is a collection that ____.
A.does not allow elements to be inserted in any position.
B.only allows items to be added at one end and removed at the other end.
C.manages associations between keys and values.
D.should be used when you need to remember the order of elements in the collection.

Question 14

A collection without an intrinsic order is called a ____.
A.queue
B.stack
C.set
D.list

Question 15

Select an appropriate expression to complete the following code segment, which is designed to print a message if the string stored in name is part of the players collection.
A.(players.contains(name))
B.(players.indexOf(name))
C.(players.search(name))
D.(players.equals(name))

Question 16

Consider the following code snippet: What will this code print when it is executed?
A.abcdefghi
B.defghiabc
C.ghiabcdef
D.abcghidef

Question 17

A binary search requires ____ access.
A.sorted
B.random
C.arbitrary
D.sequential

Question 18

A collection that allows items to be added only at one end and removed only at the other end is called a ____.
A.set
B.stack
C.queue
D.list

Question 19

What type of access does a LinkedList provide for its elements?
A.sorted
B.sequential
C.random
D.semi-random

Question 20

A collection that remembers the order of items, and allows items to be added and removed only at one end is called a ____.
A.queue
B.stack
C.list
D.set

Question 21

Which Java package contains the LinkedList class?
A.java.lang
B.java.io
C.java.collections
D.java.util

Question 22

Which method is NOT part of the ListIterator interface?
A.hasPrevious
B.hasMore
C.add
D.hasNext

Question 23

Select an appropriate expression to complete the following method, which is designed to visit the elements in theList and replace each occurrence of the string "hello" with the string "goodbye".
A.iterator.next() = "goodbye";
B.iterator.previous("goodbye");
C.iterator.replace("hello", "goodbye");
D.iterator.set("goodbye");

Question 24

When using a list iterator, on which condition will the IllegalStateException be thrown?
A.Calling next after calling previous.
B.Calling remove after calling previous.
C.Calling remove after calling remove.
D.Calling remove after calling next.

Question 25

Assume you are using a doubly-linked list data structure with many nodes.What is the minimum number of node references that are required to be modified to remove a node from the middle of the list? Consider the neighboring nodes.
A.3
B.2
C.4
D.1

Question 26

Assume you have created a linked list named myList that currently holds some number of String objects.Which of the following statements correctly removes an element from the end of myList?
A.myList.remove();
B.myList.getLast();
C.myList.pop();
D.myList.removeLast();

Question 27

Consider the code snippet shown below.Assume that employeeNames is an instance of type LinkedList. Which element(s) of employeeNames does this loop process?
A.elements meeting a condition
B.the most recently added elements
C.no elements
D.all elements

Question 28

A ____ is a data structure used for collecting a sequence of objects that allows efficient addition and removal of already-located elements in the middle of the sequence.
A.queue
B.priority queue
C.stack
D.linked list

Question 29

The nodes of a(n) ____ linked list class store two links: one to the next element and one to the previous one.
A.array
B.singly
C.randomly
D.doubly

Question 30

Assume you have created a linked list named myList that currently holds some number of String objects.Which of the following statements correctly adds a new element to the beginning of myList?
A.myList.insert("Harry");
B.myList.addFirst("Harry");
C.myList.add("Harry");
D.myList.put("Harry");

Question 31

You use a(n) ____ to access elements inside a linked list.
A.queue
B.accessor
C.list iterator
D.index

Question 32

When using the add method of the ListIterator to add an element to a linked list, which of the following statements is correct?
A.The new element is inserted before the iterator position, and a subsequent call to next would be unaffected.
B.The new element is inserted after the iterator position, and a subsequent call to next would return the new element.
C.The new element is inserted after the iterator position, and a subsequent call to previous would be unaffected.
D.The new element is inserted before the iterator position, and a subsequent call to next would return the new element.

Question 33

Consider the following code snippet: What will this code print when it is executed?
A.ghiabcdef
B.defghiabc
C.abcdefghi
D.abcghidef

Question 34

The term ____ is used in computer science to describe an access pattern in which the elements are accessed in arbitrary order.
A.sequential access
B.sorted access
C.arbitrary access
D.random access

Question 35

What can a generic class be parameterized for?
A.methods
B.iterators
C.type
D.properties

Question 36

When using a list iterator, on which condition will the IllegalStateException be thrown?
A.Calling remove after calling next.
B.Calling remove after calling add.
C.Calling add after calling previous.
D.Calling previous after calling previous.

Question 37

Which method is NOT part of the ListIterator interface?
A.next
B.delete
C.add
D.previous

Question 38

When using a list iterator, on which condition will the NoSuchElementException be thrown?
A.Calling next when you are past the end of the list.
B.Calling remove after calling add.
C.Calling remove after calling previous.
D.Calling next when the iterator points to the last element.

Question 39

Select an appropriate expression to complete the method below.The method should return the number of times that the string stored in name appears in theList.
A.theList.next() != null
B.iter.hasNext()
C.theList.hasNext()
D.iter.next() != null

Question 40

Select an appropriate expression to complete the following code segment, which is designed to print a message if the string stored in name is the first element of the players linked list.
A.(players.getFirst().equals(name))
B.(players[0].equals(name))
C.(players.contains(name))
D.(players.indexOf(name) == 1)

Question 41

Which of the following statements about manipulating objects in a map is NOT correct?
A.Use the remove method to remove a value from the map.
B.Use the get method to retrieve a value from the map.
C.Use the keyset method to get the set of keys for the map.
D.Use the add method to add a new element to the map.

Question 42

Assume that you have declared a set named mySet to hold String elements.Which of the following statements will correctly delete an element from mySet?
A.mySet.delete("apple");
B.mySet.remove("apple");
C.mySet.get("apple");
D.mySet.pop("apple");

Question 43

Select an appropriate declaration to complete the following code segment, which is designed to read strings from standard input and display them in increasing alphabetical order, excluding any duplicates.
A.LinkedList words = new LinkedList<>();
B.Set words = new TreeSet<>();
C.Set words = new Set<>();
D.Set words = new HashSet<>();

Question 44

Which of the following statements about hash tables is NOT correct?
A.Elements are grouped into smaller collections that share the same characteristic.
B.You can form hash tables holding objects of type String.
C.The value used to locate an element in a hash table is called a hash code.
D.You can add an element to a specific position within a hash table.

Question 45

Complete the following code, which is intended to print out all key/value pairs in a map named myMap that contains String data for student IDs and names:
A.String name = myMap.next(aKey);
B.String name = MapKeySet.get(aKey);
C.String name = myMap.get(aKey);
D.String name = MapKeySet.next(aKey);

Question 46

Consider the following code snippet: What will be printed when this code is executed?
A.[Mary, John, Robert, Sue]
B.[John, Robert, Sue]
C.[Mary, Robert, Sue]
D.[Mary, John, Sue]

Question 47

Assume that you have declared a map named myMap to hold String values with Integer keys.Which of the following statements will correctly delete an association from myMap?
A.myMap.remove(3);
B.myMap.remove("apple");
C.myMap.delete(3);
D.myMap.pop(3);

Question 48

In a linked list data structure, when does the reference to the first node need to be updated?
I inserting into an empty list
II deleting from a list with one node
III deleting an inner node
A.I and II only
B.I only
C.II only
D.III only

Question 49

Which of the following statements about the TreeSet class is NOT correct?
A.Elements are stored in nodes.
B.Elements are arranged in linear fashion.
C.To use a TreeSet, it must be possible to compare the elements.
D.Elements are stored in sorted order.

Question 50

To create a TreeSet for a class of objects, the object class must ____.
A.implement the Set interface.
B.implement the Comparable interface.
C.create an iterator.
D.create a Comparator object.

Question 51

Which of the following statements about manipulating objects in a set is correct?
A.If you try to remove an element that does not exist, an exception will occur.
B.If you try to add an element that already exists, an exception will occur.
C.A set iterator visits elements in the order in which the set implementation keeps them.
D.You can add an element at the position indicated by an iterator.

Question 52

Which of the following statements about manipulating objects in a map is NOT correct?
A.Use the put method to add an element to the map.
B.If you attempt to retrieve a value with a key that is not associated with any value, you will receive a null result.
C.Use the get method to retrieve a value associated with a key in the map.
D.You cannot change the value of an existing association in the map; you must delete it and re-add it with the new values.

Question 53

Select an appropriate expression to complete the following method, which is designed to return the number of elements in the parameter array numbers.If a value appears more than once, it should be counted exactly once.
A.return numbers.length - values.size();
B.return values.size();
C.return numbers.length;
D.return values.length();

Question 54

Your program uses a Map structure to store a number of user ids and corresponding email addresses.Although each user must have a unique id, two or more users can share the same email address.Assuming that all entries in the map have valid email addresses, select an appropriate expression to complete the method below, which adds a new id and email address to the map only if the id is not already in use.If the id is already in use, an error message is printed.
A.!currentEmail.equals(email)
B.currentEmail.equals(email)
C.currentEmail != null
D.currentEmail == null

Question 55

Assume that you have declared a map named myMap to hold String values with Integer keys.Which of the following statements will correctly retrieve the value associated with a key from myMap?
A.myMap.peek(3);
B.myMap.get("apple");
C.myMap.peek("apple");
D.myMap.get(3);

Question 56

Which of the following statements about sets is correct?
A.Attempting to remove an element that is not in the set generates an exception.
B.You can add an element to a specific position within a set.
C.A set is a collection of unique elements organized for efficiency.
D.A set allows duplicate values.

Question 57

Assume that you have declared a set named mySet to hold String elements.Which of the following statements will correctly insert an element into mySet?
A.mySet.put(apple");
B.mySet.insert("apple");
C.mySet.add("apple");
D.mySet.push("apple");

Question 58

Which of the following statements about manipulating objects in a set is correct?
A.A set iterator visits elements in the order in which they were added to the set.
B.You can remove an element at the position indicated by an iterator.
C.If you try to add an element that already exists, an exception will occur.
D.You can add an element at the position indicated by an iterator.

Question 59

Assume that you have declared a map named myMap to hold String values with Integer keys.Which of the following statements will correctly add an association into myMap?
A.myMap.insert(3, "apple");
B.myMap.add(3, "apple");
C.myMap.put(3, "apple");
D.myMap.push(3, "apple");

Question 60

Complete the following code, which is intended to print out all key/value pairs in a map named myMap that contains String data for student IDs and names:
A.Map mapKeySet = myMap.keySet();
B.Set mapKeySet = myMap.keySet();
C.Set mapKeySet = myMap.keySet();
D.Set mapKeySet = myMap.getKeySet();

Question 61

Consider the following code snippet:
Map scores;
You expect to retrieve elements randomly by key, and want fastest retrieval times.Which of the following statements will create a structure to support this?
A.scores = new HashMap<>;
B.scores = new Map<>;
C.scores = new TreeMap<>;
D.scores = new TreeSet<>;

Question 62

What operation is least efficient in a LinkedList?
A.Linear traversal step.
B.Random access of an element.
C.Adding an element in a position that has already been located.
D.Removing an element when the element's position has already been located.

Question 63

You need to write a program to simulate the effect of adding an additional cashier in a supermarket to reduce the length of time customers must wait to check out.Which data structure would be most appropriate to simulate the waiting customers?
A.map
B.stack
C.linked list
D.queue

Question 64

You need to access values in objects by a key that is not part of the object.Which collection type should you use?
A.Hashtable
B.ArrayList
C.Map
D.Queue

Question 65

You want to enumerate all of the keys in a map named myMap whose keys are type String.Which of the following statements will allow you to do this?
A.Set keySet = myMap.getKeySet(); for (String key : keySet) {...}
B.Set keySet = myMap.keySet(); for (String key : keySet) {...}
C.Set keySet = myMap.keys(); for (String key : keySet) {...}
D.Set keySet = myMap.getKeys(); for (String key : keySet) {...}

Question 66

You need to access values by an integer position.Which collection type should you use?
A.Queue
B.Map
C.Hashtable
D.ArrayList

Question 67

You need to access values using a key, and the keys must be sorted.Which collection type should you use?
A.Queue
B.TreeMap
C.HashMap
D.ArrayList

Question 68

Which of the following algorithms would be efficiently executed on an ArrayList?
A.remove first n / 2 elements from a list of n elements
B.add 1 element to the middle of a list with n elements
C.add n / 2 elements to a list with n / 2 elements
D.read n / 2 elements in random order from a list of n elements

Question 69

Which of the following statements about hash functions is NOT correct?
A.Using a prime number as a hash multiplier will produce better hash codes.
B.If you supply your own hashCode method for a class, it must be compatible with that class's equals method.
C.A good hash function will minimize the number of objects that are assigned the same hash code.
D.A hash function produces a unique integer-valued hash code value for each distinct object.

Question 70

An Undo feature in a word processor program that allows you to reverse a previously completed command is probably implemented using which structure type?
A.stack
B.queue
C.hash table
D.linked list

Question 71

Assume that you have declared a stack named myStack to hold String elements.Which of the following statements will correctly add an element to myStack?
A.myStack.addItem("apple");
B.myStack.put("apple");
C.myStack.insert("apple");
D.myStack.push("apple");

Question 72

Which data structure would best be used for storing a set of numbers and sorting them in ascending order?
A.queue
B.array
C.stack
D.list

Question 73

You intend to use a hash set with your own object class.Which of the following statements is correct?
A.You cannot override the hashCode method in the Object class.
B.You can use the hash method of the Objects class to create your own hashCode method by combining the hash codes for the instance variables.
C.You can override the hash method for your class provided that it is compatible with its equals method.
D.Your class's hashCode method does not need to be compatible with its equals method.

Question 74

You need to access values in the opposite order in which they were added (last in, first out), and not randomly.Which collection type should you use?
A.Hashtable
B.Map
C.Queue
D.Stack

Question 75

Using the merge method of the Map interface, which statement correctly updates the wordCount map of type Map to count all of the occurrences of a word in a file?
A.wordCount.merge(word, 1, (k,v) -> v + 1);
B.word.merge(wordCount,(k,v) -> v + 1);
C.word.merge(wordCount, 1, (k,v) -> v + 1);
D.wordCount.merge(word,(k,v) -> v + 1);

Question 76

You need to access values in the order in which they were added (first in, first out), and not randomly.Which collection type should you use?
A.Queue
B.Map
C.Stack
D.Hashtable

Question 77

Consider the following code snippet:
Map scores;
If you need to visit the keys in sorted order, which of the following statements will create a structure to support this?
A.scores = new HashTable<>;
B.scores = new HashMap<>;
C.scores = new TreeMap<>;
D.scores = new Map<>;

Question 78

Using the merge method of the Map interface, which statement correctly updates the salesTotalByDept map of type Map to update the sales total for a dept by an integer sales value?
A.salesTotalByDept.merge(dept, sales,(d,s) -> s + 1);
B.sales.merge(salesTotalByDept, dept, (d,s) -> s + sales);
C.dept.merge(salesTotalByDept, sales, (d,s) -> s + sales);
D.salesTotalByDept.merge(dept, sales, (d,s) -> s + sales);

Question 79

Which of the following statements about stacks is correct?
A.A stack implements random retrieval.
B.A stack implements last-in, first-out retrieval.
C.A stack stores elements in sorted order.
D.A stack implements first-in, first-out retrieval.

Question 80

Which of the following correctly declares a stack that will hold String elements?
A.Stack s = new Stack<>();
B.Stack s = new Stack<>();
C.String s = new Stack();
D.String s = new Stack<>();