Question 1

Which of the following performs a boxing conversion?
A)int x = 7;
B)Integer x = 7;
C)Neither of the above.
D)Both of the above.

Accepted Answer

Boxing conversion refers to the process of converting a primitive data type into a corresponding wrapper class object. In this case, Integer is the wrapper class for primitive int, making option B the correct choice as it performs a boxing conversion by creating an Integer object from the primitive value 7. Option A does not perform a boxing conversion, as it simply assigns the primitive value 7 to an int variable.

Question 2

Interface Collection contains __________ operations (i.e. ,operations performed on the entire collection).
A)aggregate.
B)composite.
C)integral.
D)bulk.

Accepted Answer

The correct term is "bulk operations," which are operations that operate on the entire collection rather than individual elements.

Question 3

The collections framework algorithms are __________,i.e. ,each of these algorithms can operate on objects that offer given interfaces without concern to the underlying implementations.
A)stable.
B)lexicographical.
C)polymorphic.
D)implementation dependent.

Accepted Answer

The collections framework algorithms are polymorphic, which means they can operate on objects that offer given interfaces without concern to the underlying implementations. This allows for increased flexibility and code reusability.

Question 4

LinkedList method listIterator returns a(n)__________.
A)Iterator.
B)List.
C)sub list.
D)bidirectional iterator.

Accepted Answer

The listIterator method returns a bidirectional iterator, which allows for both forward and backward iteration in a LinkedList.

Question 5

Java SE 7 supports type inferencing with the <> notation in statements that declare and create generic type variables and objects.For example,the following line: List< String > list = new ArrayList< String >(); Can be written as: A)List<> list = new ArrayList<>(); B)List<> list = new ArrayList< String >(); C)List< String > list = new ArrayList<>(); D)List< String > list = new ArrayList();

Accepted Answer

The best choice is C because it specifies the type of the objects in the list as String and also uses the <> notation for type inferencing for the ArrayList object. The other options either do not specify the type of objects in the list or include unnecessary information in the declaration.

Question 6

__________ allows a program to walk through the collection and remove elements from the collection.
A)Set.
B)Queue.
C)Iterator.h.List.

Accepted Answer

Iterators are objects that allow traversal of a collection while exposing its elements. Using an iterator, we can traverse through the collection and remove elements from the collection. This feature is not available in Set or Queue. List can have an iterator to walk through the collection.

Question 7

Which statement is false?
A)When a List is backed up with an array,any modifications made through the List view change the array.
B)When a List is backed up with an array,any modifications made to the array change the List view.
C)The only operation permitted on the view returned by Arrays method asList is delete,which deletes the value from the view and the backing array.
D)Adding elements to the view returned by Arrays method asList results in an UnsupportedOperationException.

Accepted Answer

The view returned by Arrays.asList does not support the add or remove operations, so the statement that only delete is permitted is false.

Question 8

The classes and interfaces which comprise the collections framework are members of package ________.
A)java.util.
B)javax.swing.
C)java.collections.
D)java.collection.

Accepted Answer

The collections framework is a part of java.util package. This package contains the classes and interfaces required for implementing various collections like List, Set, Map etc.

Question 9

Comparator method compare should return ________ if the first argument is greater than the second argument.
A)a positive int value.
B)zero.
C)a negative int value.
D)a String.

Accepted Answer

A comparator method compare should return a positive int value if the first argument is greater than the second argument. This is because the compare method is designed to be used with sorting algorithms that expect a positive, negative, or zero value to indicate the order of the two elements being compared. A positive value indicates that the first element should come after the second element in the sorted list.

Question 10

Which of the following performs an unboxing conversion? Assume x refers to an Integer object.
A)int y = x;
B)Integer y = x;
C)Neither of the above.
D)Both of the above.

Accepted Answer

An unboxing conversion is performed when an object of a wrapper class (Integer in this case) is converted to its corresponding primitive type (int in this case). Therefore, option A performs an unboxing conversion. Option B assigns an Integer object to another Integer object, which does not involve any conversion.

Question 11

Collections method ___________ returns a Comparator object that orders the collection's elements in reverse order.
A)rotate.
B)shuffle.
C)reverse.
D)reverseOrder.

Accepted Answer

The method reverseOrder() returns a Comparator object that orders the collection's elements in reverse order.

Question 12

Which statement is false?
A)A List is an ordered Collection.
B)A List cannot contain duplicate elements.
C)A List is sometimes called a sequence.
D)Lists are zero based.

Accepted Answer

A List can contain duplicate elements. The only requirement for a List is that it maintains an ordered sequence.

Question 13

Which statement is false?
A)A ListIterator accesses the elements of a List.
B)Class ArrayList is a fixed-size array.
C)A LinkedList is a linked list implementation of a List.
D)ArrayLists execute faster than Vectors because they are not thread safe.

Accepted Answer

ArrayList is a resizable array implementation of List, not a fixed-size array.

Question 14

Algorithm __________ randomly orders a List's elements.
A)randomShuffle.
B)randomPlacement.
C)fiftyTwoCardPickup.
D)shuffle.

Accepted Answer

The correct algorithm to randomly order a List's elements is the shuffle algorithm. This algorithm shuffles the elements in place, meaning the original List is modified to have its elements in a random order. Option A, randomShuffle, would also work but is not a standard built-in algorithm in most programming languages. Option B, randomPlacement, is not a known algorithm for shuffling a list. Option C, fiftyTwoCardPickup, is not an algorithm for shuffling a list but a game where cards are thrown into the air and left for someone to clean up.

Question 15

Which of these is not an example of a "real-life" collection?
A)The cards you hold in a card game.
B)Your favorite songs stored in your computer.
C)The players on a soccer team.
D)The number of pages in a book.

Accepted Answer

The number of pages in a book is not an example of a "real-life" collection as it is simply a numerical value and not a group of tangible or intangible objects that share a common characteristic. A collection typically refers to a group of physical or digital items that are curated and selected based on a specific theme or purpose. The cards in a card game, favorite songs in a computer, and players on a soccer team are all examples of real-life collections.

Question 16

Which statement is false?
A)A collection is an object that can hold references to other objects.
B)The collection interfaces declare the operations that can be performed on each type of collection.
C)Unfortunately,collections discourage software reuse because they are non-portable.
D)Collections are carefully constructed for rapid execution and efficient use of memory.

Accepted Answer

This statement is false because collections actually encourage software reuse and portability by providing standard interfaces and implementations that can be used across different platforms and programming languages.

Question 17

Iterator method __________ determines whether the Collection contains more elements.
A)hasNext.
B)next.
C)contains.
D)containsNext.

Accepted Answer

The iterator method `hasNext` returns a boolean value indicating whether there are more elements in the collection. This method is specifically designed to check for the presence of additional elements, whereas `next` actually retrieves the next element in the iteration. `contains` is a method specific to the Collection interface that checks whether a particular object is contained within the collection, and `containsNext` is not a valid method at all.

Question 18

Which statement is false?
A)Each primitive type has a corresponding type-wrapper class.
B)The type-wrapper classes enable you to manipulate primitive-type values as objects.
C)Type-wrapper classes are final,so you cannot extend them.
D)The methods for primitive types correspond to the methods for the corresponding type-wrapper classes.

Accepted Answer

The methods for primitive types do not correspond to the methods for the corresponding type-wrapper classes because primitive types themselves do not have methods in Java. Type-wrapper classes provide methods to manipulate the values, but primitive types are manipulated directly with operators and cannot have methods called on them.

Question 19

Which of the following does not implement interface List?
A)ArrayList.
B)LinkedList.
C)Vector.
D)ListIterator.

Accepted Answer

ListIterator is not a collection class and does not implement the List interface. It is a helper class that allows iterating over the elements in a list. The other options (ArrayList, LinkedList, Vector) are all implementations of the List interface.

Question 20

Collections method sort that accepts a List as an argument sorts the elements of a List,which must implement the __________ interface.
A)Comparable.
B)Comparator.
C)Compare.
D)Ordering.

Accepted Answer

The Collections method sort requires the elements of the List to implement the Comparable interface, which provides a natural ordering for the elements. This allows the sort algorithm to compare elements and arrange them in ascending or descending order. If the List does not implement Comparable, a ClassCastException will be thrown at runtime. Therefore, the best choice is A. B is incorrect because a Comparator can be used to sort a List only with the overloaded version of sort that accepts a Comparator as an argument. C and D are not valid Java interfaces.

Quiz 20: Generic Collections

Which of the following performs a boxing conversion?

Interface Collection contains __________ operations (i.e. ,operations performed on the entire collection) .

The collections framework algorithms are __________,i.e. ,each of these algorithms can operate on objects that offer given interfaces without concern to the underlying implementations.

LinkedList method listIterator returns a(n) __________.

Java SE 7 supports type inferencing with the <> notation in statements that declare and create generic type variables and objects.For example,the following line: List< String > list = new ArrayList< String >() ; Can be written as:

__________ allows a program to walk through the collection and remove elements from the collection.

Which statement is false?

The classes and interfaces which comprise the collections framework are members of package ________.

Comparator method compare should return ________ if the first argument is greater than the second argument.

Which of the following performs an unboxing conversion? Assume x refers to an Integer object.

Collections method ___________ returns a Comparator object that orders the collection's elements in reverse order.

Which statement is false?

Which statement is false?

Algorithm __________ randomly orders a List's elements.

Which of these is not an example of a "real-life" collection?

Which statement is false?

Iterator method __________ determines whether the Collection contains more elements.

Which statement is false?

Which of the following does not implement interface List?

Collections method sort that accepts a List as an argument sorts the elements of a List,which must implement the __________ interface.