Deck 3: Object-Oriented Programming, Part 1: Using Classes

Question 1

The automatic conversion from a primitive numeric type to its wrapper class is called:

A) boxing.
B) unboxing.
C) autoboxing.

Answer 1

C

Question 2

The automatic conversion from a numeric wrapper class to the corresponding primitive numeric type is called:

A) boxing.
B) unboxing.
C) autoboxing.

Answer 2

B

Question 3

A way to convert a primitive data type into an object is to use __________ classes.

Answer 3

wrapper

Question 4

In order to test if a character is a digit, we can use the Character class and its ________ method.

Question 5

The identifier of the object is called the:

A) instance variable.
B) instantiating object.
C) object reference.
D) instance of the class.

Question 6

Object references can refer to any object of its class.

Question 7

What is the relationship between an object and a class?

A) An object is used to debug a class.
B) A class describes a generic template for creating, or instantiating, objects.
C) A class can refer to any object of its object reference.
D) Object diagrams can refer to any object of its class.

Question 8

DaysOffWork ( ) a default constructor because its parameter list is empty.

Question 9

The argument list of a constructor consists of a comma-separated list of initial data values to assign to the object.

Question 10

The mutators are the _______ methods.

A) set
B) get
C) let
D) All of these are correct.

Question 11

nextDay ( ) can be used in an expression (the method header is public void nextDay( ) ).

Question 12

Java does not provide support for explicitly deleting an object.

Question 13

Java would generate a compiler error and a run-time error if you attempt to call a method using an object reference whose value is null.

Question 14

A Scanner object divides its input into sequences of characters called:

A) delimiters.
B) white spaces.
C) tokens.
D) object references.

Question 15

When writing code, you can include two forward slashes for a comment and then later replace them with back slashes to uncomment.

Question 16

Many of the commonly used classes, such as String and Math, reside in the java.lang package.

Question 17

indexOf methods are useful for searching a String for a specific String or character.

Question 18

In which package is the class Math?

A) java.lang
B) java.number
C) java.math
D) java.text
E) java.util

Question 19

Which keyword allows you to use a Java class inside a program?

A) include
B) class
C) import
D) package
E) with

Question 20

The charAt method returns the character at a particular index in a String.

Question 21

The constructor for the Random class is:

A) Random ( ).
B) int (Random).
C) nextRandom.
D) nullRandom.

Question 22

Computers are deterministic, so given a specific input to a specific set of instructions, a computer will always produce the same output.

Question 23

In Math.abs( -5 ), abs is a static method.

Question 24

The System class is in the java.lang package.

Question 25

What is the value of the expression Math.sqrt( 4 )?

A) 2.0
B) 0.0
C) 4.0
D) 1.0

Question 26

What is the value of the expression Math.pow( 3, 2 )?

A) 2.0
B) 3.0
C) 6.0
D) 8.0
E) 9.0

Question 27

We can instantiate an object from the NumberFormat class using the new keyword.

Question 28

Wrapper classes define an instance variable of a primitive data type and provide useful methods for converting the primitive data types into objects.

Question 29

In what package is the class Scanner?

A) java.lang
B) java.scanner
C) java.io
D) java.text
E) java.util

Question 30

What is the output of this code sequence?
String word = "Java";
System.out.println( word.length( ) );

A) 0
B) 1
C) 4
D) 5

Question 31

What is the output of this code sequence?
String word = "Java";
System.out.println( word.charAt( 1 ) );

A) J
B) a
C) v
D) "

Question 32

When an object reference is first declared, its value is null.

Question 33

Using a null object reference to call a method will not generate an error.

Question 34

String is in the java.string package.

Question 35

The length method of the String class takes no argument and returns an int.

Question 36

The first index of a String is 1.

Question 37

The DecimalFormat can be used to format a number by specifying a number of digits after the decimal point.

Question 38

The wrapper class for char is Char.

Question 39

The _________ class is used to get user input from the Java console.

Question 40

API stands for __________.

Question 41

The special method called when instantiating an object is a(n) __________.

Question 42

What keyword is used when instantiating an object?

A) Create
B) =
C) new
D) Object
E) is

Question 43

In which package is the class DecimalFormat?

A) java.lang
B) java.number
C) java.format
D) java.text
E) java.util

Question 44

The data type of System.out is:

A) Print.
B) PrintStream.
C) System.
D) Out.
E) IO.

Question 45

In which package is the class NumberFormat?

A) java.lang
B) java.number
C) java.format
D) java.text
E) java.util

Question 46

By convention, method names, instance variables, and object names start with a lowercase letter.

Question 47

The parameter list of a default constructor is empty.

Question 48

E and PI are two static data members of the Math class.

Question 49

The accessors are the get methods.

Question 50

The data associated with an object of a class are called __________.

Question 51

The operations for a class are called __________.

Question 52

The API of class methods has the keyword __________ before the return type.

Question 53

Java classes are organized in __________.

Question 54

One can generate random numbers using the ___________ class.

Question 55

What are the main benefits of using classes?

Question 56

Write a Java statement to import the DecimalFormat class from the appropriate package.

Question 57

Give one reason you would use the NumberFormat class.

Question 58

What does the following code do?
String s = "Hello";
s = s.toUpperCase( );

Question 59

Identify when you would use nextLine( ) in the Scanner class.

Question 60

Why do you think the String class is in the java.lang package?

Question 61

What would you automatically use to assign the char variable to a Character object reference?

Question 62

Which methods of the String class would you use to retrieve the user name from an email address whose format is username@provider?