Deck 3: Implementing Classes

Question 1

Private instance variables ___.

A) can only be accessed by methods of a different class
B) can only be accessed by methods of the same class
C) cannot be accessed by methods of the same class
D) can only be accessed by the constructor of the class

Answer 1

B

Question 2

An instance variable declaration consists of which of the following parts?

A) the return type, the name of the method, and a list of the parameters (if any).
B) an access specifier, the type of the instance variable, and the name of the instance variable.
C) an access specifier, a list of the parameters (if any), and the body of the method.
D) the type of the instance variable, an access specifier, a list of the parameters (if any), and the body of the method.

Answer 2

B

Question 3

What is the return type of the println method of the PrintStream class?

A) void
B) public
C) String
D) double

Answer 3

A

Question 4

A class declaration consists of which of the following parts?

A) an access specifier, the keyword class, the name of the class, declarations for instance variables, constructors, and methods
B) an access specifier, a return type, a method name, a list of the parameters (if any), and the body of the method
C) the keyword class, the name of the class, declarations for instance variables, constructors, and methods
D) an access specifier, the name of the class, a list of the parameters (if any), and the body of the constructor

Question 5

What contains the instructions to initialize the instance variables of an object?

A) constructor
B) access specifier
C) initializer
D) type name

Question 6

The black boxes from which a program is manufactured are called ___.

A) objects
B) access specifiers
C) methods
D) instance variables

Question 7

What is the name of the instance variable for a BankAccount object?

A) makeDeposit
B) makeWithdrawl
C) getBalance
D) balance

Question 8

A method header consists of which of the following parts?

A) the return type, the name of the method, and a list of the parameters (if any)
B) an access specifier, the type of the instance variable, and the name of the instance variable
C) the type of the instance variable, an access specifier, and a list of the parameters (if any)
D) an access specifier, a return type, a method name, and a list of the parameters (if any)

Question 9

The name of the constructor is always the same as the name of the __.

A) access specifier
B) class
C) instance variable
D) parameter variable

Question 10

What is the process of hiding object data and providing methods for data access called?

A) documentation
B) encapsulation
C) instantiation
D) abstraction

Question 11

Consider the following method comment and method header: /**
Converts from a source measurement to a target measurement.
@param _______________ the measurement
@return the input value converted to the target unit
*/
Public double convertTo(double fromMeasurement) { . . . }
Fill in the blank.

A) return
B) fromMeasurement
C) double
D) convertTo

Question 12

What does an object store its data in?

A) files
B) methods
C) instance variables
D) access specifiers

Question 13

Encapsulation allows a programmer to use a class without having to know its ____.

A) interface
B) name
C) methods
D) implementation

Question 14

Each object of a class has its own set of ___.

A) methods
B) instance variables
C) constructors
D) classes

Question 15

You should declare all instance variables as ___.

A) protected
B) class
C) public
D) private

Question 16

What contains the instructions to initialize the instance variables of an object?

A) constructor
B) access specifier
C) initializer
D) type name

Question 17

What is the return type of a constructor?

A) void
B) A constructor does not have a return type.
C) private
D) public

Question 18

What statement is used to specify the value that a method gives back to its caller?

A) new
B) public
C) private
D) return

Question 19

Information hiding makes it simpler for the implementor of a class to _____.

A) change the private implementation
B) change the method headers
C) change the name of the class
D) change the public interface

Question 20

Consider the following method comment and method header: /**
Converts from a source measurement to a target measurement.
__________ fromMeasurement the measurement
@return the input value converted to the target unit
*/
Public double convertTo(double fromMeasurement) { . . . }
Fill in the blank.

A) @param
B) param
C) @parameter
D) parameter

Question 21

What is the name of the utility that formats comments into a set of documents that you can view in a Web browser?

A) javadoc
B) javac
C) javad
D) java

Question 22

We want to change the BankAccount class so that all accounts will have a monthly fee. When a BankAccount is created, its monthly fee is set and cannot be changed. The instance variable monthlyFee will hold the monthly fee. Which of the following methods deducts the value of the monthly fee from the account? a. public void chargeFee()
{
Balance = balance - monthlyFee;
}
B) public void chargeFee()
{
InitialBalance = initialBalance - monthlyFee;
}
C) public void chargeFee()
{
Balance = monthlyFee;
}
D) public void chargeFee()
{
Balance - monthlyFee;
}

Question 23

We want to create a class that represents a geometric sequence. A geometric sequence is a sequence of numbers that begin at some value and then multiplies each value by some constant to get the next value. For example, the geometric sequence 1, 2, 4, 8, 16 starts at 1 and multiplies each term by 2 to get the next. The geometric sequence 10.8, 5.4, 2.7, 1.35 starts at 10.8 and multiplies each term by 0.5 to get the next. The basic framework of a geometric sequence class is below: public class GeometricSequence
{
Private double initialValue;
Private double multiplier;
}
What should the body of the constructor be?

A) initialValue = initial; multiplier = mult;
B) initial = initialValue; mult = multiplier;
C) double initialValue = initial; double multiplier = mult;
D) double initial = initialValue; double mult = multiplier;

Question 24

What are the operations that any programmer can use to create and manipulate objects of the class called?

A) public implementation
B) public interface
C) private implementation
D) private interface

Question 25

The public constructors and methods of a class form the public _____ of the class.

A) interface
B) initialization
C) implementation
D) encapsulation

Question 26

You should provide documentation comments for ___.

A) only classes
B) only methods with parameters
C) every class, every method, every parameter, and every return value
D) only methods with return values

Question 27

Which of the following corresponds to a valid constructor header for the Player class?

A) public Player()
B) private Player
C) public void Player()
D) private void Player()

Question 28

Consider the following method comment and method header: /**
Converts from a source measurement to a target measurement.
@param fromMeasurement the measurement
__________ the input value converted to the target unit
*/
Public double convertTo(double fromMeasurement) { . . . }
Fill in the blank.

A) return double
B) return
C) @return double
D) @return

Question 29

We want to change the BankAccount class so that all accounts will have a monthly fee. When a BankAccount is created, its monthly fee is set and cannot be changed. Which of the following will properly define the instance variable monthlyFee that holds the monthly fee?

A) monthlyFee: double;
B) instance var monthlyFee;
C)private double monthlyFee;
D)private field monthlyFee;

Question 30

Which of the following statements is true about constructors?

A) Providing a constructor for a class is optional.
B) You can only provide one constructor for a class.
C) The body of the constructor must initialize all instance variables or the constructor will not successfully compile.
D) A constructor has a void return type.

Question 31

We want to change the BankAccount class so that all accounts will have a monthly fee. When a BankAccount is created, its monthly fee is set and cannot be changed. The instance variable monthlyFee will hold the monthly fee. Which of the following constructors properly sets the monthly fee to a default value of 20? a. public BankAccount (double initialBalance)
{
Balance = initialBalance;
MonthlyFee = 20;
}
B) public BankAccount (double initialBalance)
{
Balance = initialBalance;
Double monthlyFee = 20;
}
C) public BankAccount (double initialBalance)
{
Balance = initialBalance;
MonthlyFee = initialBalance - 20;
}
D) public BankAccount (double initialBalance)
{
Balance = initialBalance - 20;
}

Question 32

What is the name of the constructor for the BankAccount class?

A) BankAccount
B) deposit
C) balance
D) withdraw

Question 33

Documentation ___ can be used to describe the classes and public methods of programs.

A) components
B) comments
C) constants
D) commands

Question 34

We want to create a class that represents a geometric sequence. A geometric sequence is a sequence of numbers that begin at some value and then multiplies each value by some constant to get the next value. For example, the geometric sequence 1, 2, 4, 8, 16 starts at 1 and multiplies each term by 2 to get the next. The geometric sequence 10.8, 5.4, 2.7, 1.35 starts at 10.8 and multiplies each term by 0.5 to get the next. The basic framework of a geometric sequence class is below: public class GeometricSequence
{
Private double initialValue;
Private double multiplier;
}
We want to create a geometric sequence using code like:
GeometricSequence first = new GeometricSequence (1, 2);
// Creates 1, 2, 4, 8, 16…
GeometricSequence second = new GeometricSequence (10.8, 0.5);
// Creates 10.8, 5.4, 2.7, 1.35 …
Which of the constructor specifications below will allow this code to behave as desired?

A) public void GeometricSequence(double initial, double mult)
B) public GeometricSequence init(double initial, double mult)
C) public GeometricSequence GeometricSequence(double initial, double mult)
D) public GeometricSequence(double initial, double mult)

Question 35

We want to create a class that represents a geometric sequence. A geometric sequence is a sequence of numbers that begin at some value and then multiplies each value by some constant to get the next value. For example, the geometric sequence 1, 2, 4, 8, 16 starts at 1 and multiplies each term by 2 to get the next. The geometric sequence 10.8, 5.4, 2.7, 1.35 starts at 10.8 and multiplies each term by 0.5 to get the next. The basic framework of a geometric sequence class is below: public class GeometricSequence
{
Private double initialValue;
Private double multiplier;
}
We want to produce elements of the geometric sequence using code like:
System.out.println (first.next()); // Prints 1 and advances
System.out.println (first.next()); // Prints 2 and advances
System.out.println (first.next()); // Prints 4 and advances
System.out.println (first.next()); // Prints 8 and advances
System.out.println (second.next()); //Prints 10.8 and advances
System.out.println (second.next()); //Prints 5.4 and advances
System.out.println (second.next()); //Prints 2.7 and advances
Which of the method specifications below will allow this code to behave as desired?

A) public next() : double
B) public int next()
C) public void next(double result)
D) public double next()

Question 36

Which of the following is a valid constructor header for the Player class that accepts the player name as a parameter?

A) public void Player(String playerName)
B) private Player(playerName)
C) private void Player(playerName)
D) public Player(String playerName)

Question 37

We want to create a class that represents a geometric sequence. A geometric sequence is a sequence of numbers that begin at some value and then multiplies each value by some constant to get the next value. For example, the geometric sequence 1, 2, 4, 8, 16 starts at 1 and multiplies each term by 2 to get the next. The geometric sequence 10.8, 5.4, 2.7, 1.35 starts at 10.8 and multiplies each term by 0.5 to get the next. The basic framework of a geometric sequence class is below: public class GeometricSequence
{
Private double initialValue;
Private double multiplier;
}
We want to produce elements of the geometric sequence using codeSystem.out.println (first.next()); // Prints 1 and advances
System.out.println (first.next()); // Prints 2 and advances
System.out.println (first.next()); // Prints 4 and advances
System.out.println (first.next()); // Prints 8 and advances
System.out.println (second.next()); //Prints 10.8 and advances
System.out.println (second.next()); //Prints 5.4 and advances
System.out.println (second.next()); //Prints 2.7 and advances
What should the body of the next method be?

A) double result = initialValue; initialValue = initialValue * multiplier;
Return result;
B) return initialValue; initialValue = initialValue * multiplier;
C) double result = initialValue; multiplier = initialValue * multiplier;
Return result;
D) initialValue = initialValue * multiplier; return initialValue;

Question 38

Consider the following code to declare a constructor for the Player class: public void Player(String playerName)
{
Name = playerName;
}
Which statement is true?

A) The code compiles successfully and results in the instantiation of a Player object when called.
B) The code compiles successfully but results in a compiler error in the code that calls the constructor.
C) The code does not compile.
D) The code compiles successfully but results in a run-time error in the code that calls the constructor.

Question 39

We want to change the BankAccount class so that all accounts will have a monthly fee. When a BankAccount is created, its monthly fee is set and cannot be changed. The instance variable monthlyFee will hold the monthly fee. Which of the following is the correct public interface for a constructor that sets both the initial balance and monthly fee?

A) public BankAccount (double initialBalance, monthlyFee)
B) public BankAccount (double initialBalance, double monthlyFee)
C) public BankAccount (double initialBalance) has monthlyFee
D) public BankAccount (double initialBalance) {
Double monthlyFee;
// The rest of the constructor code follows
}

Question 40

If a method has two parameters, one explicit and one implicit, and a return type of void, then the documentation comments should include:

A) One @param statement, and one @return statement
B) Two @param statements, and one @return statement
C) One @param statement, and no @return statement
D) Two @param statements, and no @return statement

Question 41

Choose the method header that goes with this method comment. /**
Gets the salary of the employee
@return the salary of the employee
*/

A) public void getSalary()
B) public void getSalary
C) public double getSalary()
D) public double getSalary

Question 42

Given this method comment, fill in the blank in the method implementation. /**
Gets the current balance of the bank account
@return the current balance
*/
Public double getBalance()
{
__________ balance;
}

A) balance
B) @return
C) double
D) return

Question 43

Given this method implementation, fill in the blank in the method comment. /**
Gets the current balance of the bank account
_________ the current balance
*/
Public double getBalance()
{
Return balance;
}

A) return
B) double
C) @return
D) balance

Question 44

Which line of code is part of the public implementation of the BankAccount class?

A) balance = balance + amount;
B) balance = balance - amount;
C) public BankAccount(double initialBalance)
D) return balance;

Question 45

Complete the following tester program by choosing the line that prints the expected outcome. public class BankAccountTester
{
Public static void main(String[] args)
{
BankAccount account = new BankAccount(1000);
Account.deposit(account.getBalance());
System.out.println(account.getBalance());
___________________
}
}

A) System.out.println("Expected: 1000");
B) System.out.println("Expected: 2000");
C) System.out.println("Expected: 2000")
D) println("Expected: 2000");

Question 46

Fill in the blank in the comment for this method header. /**
Constructs a player with the given name
_________________________________
*/
Public Player(String playerName)
) . .

A) @return the player
B) @parameter playerName the name of the player
C) @param playerName the name of the player
D) return the player

Question 47

Consider the following method header: /**
Adds interest to the bank account
_________________________________
*/
Public void addInterest(double rate)
) . .
Fill in the blank in the javadoc comment:

A) @param rate the rate of interest
B) @parameter rate the rate of interest
C) @param interestRate the rate of interest
D) @parameter interestRate the rate of interest

Question 48

Given this method comment, fill in the blank in the method implementation. /**
Constructs a bank account with a given balance
@param initialBalance the initial balance
*/
Public BankAccount(double _________)
{
Balance = initialBalance;
}

A) amount
B) parameter
C) initialBalance
D) balance

Question 49

Fill in the blank in the comment for this method header. /**
Gets the interest for the bank account
_________________________________
*/
Public double getInterest()
) . .

A) @return double the interest
B) return the interest
C) @return the interest
D) return double the interest

Question 50

Given this method implementation, fill in the blank in the method comment. /**
Withdraws money from the bank account
_________ amount the amount to withdraw
*/
Public void withdraw(double amount)
{
Balance = balance - amount;
}

A) parameter
B) @param
C) param
D) @parameter

Question 51

Consider the following method header for the BankAccount class: public void addInterest(double rate)
{
______________________________________
}
Fill in the blank in the method body.

A) balance = balance * (1 + rate);
B) balance = balance * rate;
C) balance = balance * (1 + interestRate);
D) balance = balance * interestRate;

Question 52

What is a tester class?

A) A class that constructs objects.
B) A class that invokes one or more methods.
C) A class that is named Tester.
D) A class with a main method that contains statements to run methods of another class.

Question 53

What verifies that a class works correctly in isolation, outside a complete program?

A) unit test
B) encapsulation
C) abstraction
D) enumeration

Question 54

Which line of code is part of the private implementation of the BankAccount class?

A) public BankAccount()
B) balance = balance - amount;
C) public void deposit(double amount)
D) public void withdraw(double amount)

Question 55

The private implementation of a class consists of ___.

A) instance variables and the method headers
B) local variables and the method headers
C) parameter variables and the method bodies
D) instance variables and the implementation of the constructors and methods

Question 56

When you declare a method, you also need to provide the method ____, which consists of statements that are executed when the method is called.

A) body
B) header
C) return type
D) access specifier

Question 57

Given this method comment, fill in the blank in the method implementation. /**
Deposits money into the bank account
@param amount the amount to deposit
*/
Public _____ deposit(double amount)
{
Balance = balance + amount;
}

A) double
B) void
C) return
D) null

Question 58

Fill in the blank in the following method comment. /**
Deposits money into the bank account
@param _________ the amount to deposit
*/
Public void deposit(double amount)
{
Balance = balance + amount;
}

A) amount
B) balance
C) double amount
D) money

Question 59

Choose the method header that goes with this method comment. /**
Raises the salary of the employee
@param percentRaise salary percentage raise
*/

A) public void raiseSalary(double percent)
B) public double raiseSalary(double percent)
C) public double raiseSalary(double percentRaise)
D) public void raiseSalary(double percentRaise)

Question 60

Consider the following method header for an Employee class: public void raiseSalary(double percentRaise)
{
______________________________________
}
Fill in the blank in the method body:

A) salary = salary * (1 + percentRaise);
B) salary = salary * percentRaise;
C) salary = salary * raise;
D) salary = salary * (1 + raise);

Question 61

Identify the explicit parameter of the withdraw method of the BankAccount class.

A) public
B) double
C) balance
D) amount

Question 62

Instance variables that are object references are initialized to what default value?

A) empty
B) Instance variables are not initialized to a default value.
C) null
D) nil

Question 63

What do instance variables belong to?

A) an object
B) a class
C) a method
D) a package

Question 64

A method is invoked on what type of parameter?

A) public parameter
B) explicit parameter
C) private parameter
D) implicit parameter

Question 65

When a method exits, its ____ are removed.

A) local variables
B) classes
C) comments
D) instance variables

Question 66

Assuming the following code is the body of the deposit method, what output is generated by the valid call myAccount.deposit(1000) for an account with an initial balance of 500? public void deposit(double amount)
{
System.out.println(amount);
Double newBalance = balance + amount;
Balance = newBalance;
}

A) 1500.0
B) The code fragment has a syntax error and does not compile.
C) The code fragment does not compile because the parameter variable is not initialized.
D) 1000.0

Question 67

Instance variables that are numbers are initialized to what default value?

A) Instance variables are not initialized to a default value.
B) nil
C) 0
D) null

Question 68

Assuming the following code is the body of the main method, what output is generated? BankAccount myAccount;
System.out.println(myAccount.getBalance());

A) The code fragment does not compile because the local variable is not initialized.
B) 0.0
C) The code fragment has a syntax error and does not compile.
D) 1000.0

Question 69

What is a local variable?

A) A variable that is declared in the header of a class.
B) A variable that is declared in the body of the class.
C) A variable that is declared in the header of a method.
D) A variable that is declared in the body of a method.

Question 70

What do parameters and local variables belong to?

A) an object
B) a class
C) a method
D) a package

Question 71

When are local variables initialized?

A) Local variables are initialized with a default value before a constructor is invoked.
B) Local variables are initialized when the method is called.
C) You must initialize local variables in a method body.
D) You must initialize local variables in the constructor.

Question 72

When are instance variables initialized?

A) Instance variables are initialized when the method is called.
B) Instance variables are initialized with a default value before a constructor is invoked.
C) You must initialize instance variables in the constructor.
D) You must initialize instance variables in a method body.

Question 73

What is the name of the local variable of the giveChange method of the CashRegister class?

A) amount
B) change
C) payment
D) purchase

Question 74

The use of an instance variable name inside a method denotes the instance variable of what?

A) the parameter variable
B) the access specifier
C) the explicit parameter
D) the implicit parameter

Question 75

What is a parameter variable?

A) A variable that is declared in the header of a method.
B) A variable that is declared in the body of the class.
C) A variable that is declared in the body of a method.
D) A variable that is declared in the header of a class.

Question 76

Which of the following denotes the implicit parameter?

A) void
B) this
C) extends
D) public

Question 77

What do static variables belong to?

A) a method
B) a package
C) a class
D) an object

Question 78

Which of the following is an instance variable of the CashRegister class?

A) amount
B) balance
C) change
D) purchase

Question 79

What is the name of the parameter variable of the recordPurchase method of the CashRegister class?

A) amount
B) payment
C) purchase
D) change

Question 80

Given the following constructor for the BankAccount class, what output is generated by a call to new BankAccount()?
Public BankAccount()
{
System.out.println(balance);
}

A) The code fragment has a syntax error and does not compile.
B) 1000.0
C) 0.0
D) You cannot print out the value of an uninitialized instance variable.