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CSC 331 Test 1

Terms in this set (35)

Static class variables ________.
are private

are public

are shared by all objects of a class

are final
are shared by all objects of a class
Which of the following is false?

A static method must be used to access private static instance variables.

A static method can be accessed even when no objects of its class have been instantiated.

A static method can call instance methods directly.

A static method has no this reference.
A static method can call instance methods directly.
Instance variables declared final do not or cannot ________.

cause syntax errors if used as a left-hand value

None of the above.

be initialized

be modified after they are initialized
be modified after they are initialized
A final field should also be declared ________ if it is initialized in its declaration.

protected

static

public

private
static
When no access modifier is specified for a method or variable, the method or variable ________.

is static

is public

has package access

is private
has package access
The ________ of a class are also called the public services or the public interface that the class provides to its clients.

public instance variables

All of the above.

public constructors

public methods.
public methods
The static method ________ of class String returns a formatted String.

toFormatedString

formatString

printf

format
format
Which of the following class members should usually be private?

All of the above.

Variables (or fields).

Methods.

Constructors.
Variables (or fields).
Which of the following statements is true?

Information hiding is achieved by restricting access to class members via keyword public.

The private members of a class are directly accessible to the clients of a class.

None of the above is true.

Methods and instance variables can both be either public or private.
Methods and instance variables can both be either public or private.
When must a program explicitly use the this reference?

Accessing a public variable.

Accessing an instance variable that is shadowed by a local variable.

Accessing a local variable.

Accessing a private variable.
Accessing an instance variable that is shadowed by a local variable.
Having a this reference allows ________.

a method to refer explicitly to the instance variables and other methods of the object on which the method was called

an object to reference itself
a method to refer implicitly to the instance variables and other methods of the object on which the method was called

All of the above.
All of the above.
A constructor cannot ________.
be overloaded

specify return types or return values

initialize variables to their defaults

have the same name as the class
specify return types or return values
Constructors ________.

initialize instance variables
when overloaded, are selected by number, types and order of types of parameters

when overloaded, can have identical argument lists

Both A and C.
Both A and C.
A programmer-defined constructor that has no arguments is called a(n) ________.

no-argument constructor

default constructor

null constructor

empty constructor
no-argument constructor
What happens when this is used in a constructor's body to call another
constructor of the same class if that call is not the first statement in the constructor?

A logic error occurs.

A runtime error occurs.

Nothing happens. The program compiles and runs.

A compilation error occurs.
A compilation error occurs.
When implementing a method, use the class's set and get methods to access the class's ________ data.

private.

protected.

All of the above.

public.
private
Which statement is false?

If a class's constructors all require arguments and a program attempts to call a no-argument constructor to initialize an object of the class, a compilation error occurs.

The compiler always creates a default constructor for a class.

None of the above.

A constructor can be called with no arguments only if the class does not have any constructors or if the class has a public no-argument constructor.
The compiler always creates a default constructor for a class.
Set methods are also commonly called ________ methods and get methods are also commonly called ________ methods.

accessor, mutator

mutator, accessor

query, accessor

query, mutator
mutator, accessor
Using public set methods helps provide data integrity if ________.

the instance variables are public

the methods perform validity checking

the instance variables are private

Both B and C.
Both B and C.
Composition is sometimes referred to as a(n) ________.

many-to-one relationship

has-a relationship

one-to-many relationship

is-a relationship
has-a relationship
Which of the following statements is false?

The class following the extends keyword in a class declaration is the direct superclass of the class being declared.

A subclass is often larger than its superclass.

Java uses interfaces to provide the benefits of multiple inheritance.

A superclass object is a subclass object.
A superclass object is a subclass object.
Inheritance is also known as the ________.

has-a relationship

knows-a relationship

uses-a relationship

is-a relationship
is-a relationship
Which of the following is not a superclass/subclass relationship?

Employee/Hourly Employee.

None of the above.

Vehicle/Car.

Sailboat/Tugboat.
Sailboat/Tugboat.
An advantage of inheritance is that ________.

None of the above.

objects of a subclass can be treated like objects of their superclass

all methods can be inherited

all instance variables can be uniformly accessed by subclasses and superclasses
objects of a subclass can be treated like objects of their superclass
Which of the following keywords allows a subclass to access a superclass method even when the subclass has overridden the superclass method?

base.

super.

public.

this.
super.
Using the protected keyword also gives a member ________.

block scope

private access

package access

public access
package access
Superclass methods with this level of access cannot be called from subclasses.

public.

package.

protected.

private.
private.
Which of the following statements is false?

A class's instance variables are normally declared private to enforce good software engineering.

It's often much more efficient to create a class by inheriting from a similar class than to create the class by writing every line of code the new class requires.

A class can directly inherit from class Object.

If the class you're inheriting from declares instance variables as private, the inherited class can access those instance variables directly.
If the class you're inheriting from declares instance variables as private, the inherited class can access those instance variables directly.
Every class in Java, except ________, extends an existing class.

String.

Integer

Object

Class
Object
Overriding a method differs from overloading a method because ________.

Both of the above.

overloaded methods have the same signature

overridden methods have the same signature

Neither of the above.
overridden methods have the same signature
Consider the classes below, declared in the same file:

class A {
int a;public A() {
​a = 7;
}
}
class B extends A {
int b;
public B() {​
b = 8;
}
}

Which of the statements below is false?

After the constructor for class B executes, the variable b will have the value 8.

A reference of type A can be treated as a reference of type B.

After the constructor for class B executes, the variable a will have the value 7.

Both variables a and b are instance variables.
A reference of type A can be treated as a reference of type B.
Which of the following is the superclass constructor call syntax?

None of the above.

keyword super, followed by a dot (.) .

keyword super, followed by a set of parentheses containing the superclass constructor arguments.

keyword super, followed by a dot and the superclass constructor name.
keyword super, followed by a set of parentheses containing the superclass constructor arguments.
Which superclass members are inherited by all subclasses of that superclass?

private instance variables and methods.

private constructors.

protected instance variables and methods.

protected constructors.
protected instance variables and methods.
private fields of a superclass can be accessed in a subclass ________.

by calling public or protected methods declared in the superclass

All of the above.

by calling private methods declared in the superclass

directly
by calling public or protected methods declared in the superclass
When a subclass constructor calls its superclass constructor, what happens if the superclass's constructor does not assign a value to an instance variable?

The program compiles and runs
because the instance variables are initialized to their default values.

A run-time error occurs.

A compile-time error occurs.

A syntax error occurs.
The program compiles and runs because the instance variables are initialized to their default values.
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