Question 1

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 when a value of a wrapper class is converted to its corresponding primitive type. In this case, option A performs an unboxing conversion because the value of x, which is an Integer object, is being assigned to an int variable y. Option B does not perform an unboxing conversion because y remains an Integer object.

Question 2

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

Accepted Answer

The collections framework algorithms are designed to be polymorphic, meaning they operate on objects that implement specified interfaces without concern for the underlying implementations. This allows for greater flexibility and reusability of the algorithms with different types of collections.

Question 3

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

Accepted Answer

The Comparable interface provides the natural ordering of objects, which is used by the Collections method sort to sort the List elements. Therefore, the correct choice is A. Choices B, C, and D are incorrect because they do not provide the necessary functionality for the sort method to work correctly. Comparator is used to define custom ordering of objects, Compare does not represent an interface in Java, and Ordering is a class in Guava library that provides additional functionalities for ordering objects, but is not used by the Collections method sort.

Question 4

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

Accepted Answer

The shuffle algorithm is specifically designed to randomly order elements in a List, making it the best choice. The other options are not commonly used or related to this particular task.

Question 5

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

Accepted Answer

A List can contain duplicate elements.

Question 6

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

Accepted Answer

The method listIterator returns a ListIterator, which is a type of bidirectional iterator that can traverse the LinkedList in both forward and backward directions. Therefore, the best choice for this question is D.

Question 7

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

Accepted Answer

The hasNext() method is used to check whether the Collection has more elements or not. If there are more elements, the method returns true, otherwise, it returns false.

Question 8

Which statement is false?
A)When a List is backed by an array,any modifications made through the List view change the array.
B)When a List is backed by 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 statement "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" is false. In addition to delete, the List view returned by Arrays.asList() supports other operations such as get, set, and add. However, adding elements to the List view returned by Arrays.asList() may result in an UnsupportedOperationException as the List view is fixed-size and cannot be modified.

Question 9

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 reverseOrder method returns a Comparator object that orders the collection's elements in reverse order. The rotate method moves the elements of the list by a specified distance, the shuffle method randomly shuffles the elements, and the reverse method reverses the order of the elements in place.

Question 10

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

Accepted Answer

ListIterator is not a class that implements the List interface. It is instead an interface that extends the Iterator interface, and is used specifically for iterating through lists. ArrayList, LinkedList, and Vector are all classes that implement the List interface.

Question 11

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

The Comparator method compare should return a positive int value if the first argument is greater than the second argument. This is the standard convention for Comparator implementations.

Question 12

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 does not represent a collection, but rather a quantitative feature of the book. The other options represent "real-life" collections: cards in a card game, songs in a music collection, and players on a sports team.

Question 13

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

Accepted Answer

The answer of Java supports type inferencing with the <>...

Question 14

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 15

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

Class ArrayList is a dynamic array, meaning it can grow or shrink in size during runtime.

Question 16

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

A boxing conversion is converting a primitive data type to its corresponding wrapper class. In this case, option B performs a boxing conversion by assigning the primitive int value 7 to the Integer wrapper class. Option A declares and assigns an int value but does not perform a boxing conversion.

Question 17

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)Collections discourage software reuse because they are non-portable.
D)Collections are carefully constructed for rapid execution and efficient use of memory.

Accepted Answer

Collections do not discourage software reuse as they are designed for reuse and convenient manipulation of data. They are also portable across different platforms and can be used in various programming languages.

Question 18

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

Accepted Answer

An iterator is an interface that allows a program to walk through a collection and remove elements from the collection. It provides methods like hasNext() (which returns true if there are more elements in the collection), next() (which returns the next element in the collection), and remove() (which removes the last element returned by next() from the collection). Sets, queues, and lists are different types of collections, but only the iterator can be used to remove elements from them.

Question 19

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 in Java is a part of the java.util package. This package contains all the classes and interfaces required for implementing different types of collections like List, Set, Map, etc. Therefore, option A is the correct answer. Options B, C, and D are not correct as they do not represent the package where the collections framework is present in Java.

Question 20

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.

Quiz 16: Generic Collections

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

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

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

Algorithm __________ randomly orders a List's elements.

Which statement is false?

LinkedList method listIterator returns a(n) __________.

Iterator method __________ determines whether the Collection contains more elements.

Which statement is false?

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

Which of the following does not implement interface List?

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

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

Java 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:

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

Which statement is false?

Which of the following performs a boxing conversion?

Which statement is false?

A(n) __________ allows a program to walk through the collection and remove elements from the collection.

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

Which statement is false?