Java
Instance variables declared final do not or cannot
be modified after they are initialized
Assigning a subclass reference to a superclass variable is safe ________.
because the subclass object is an object of its superclass
Private fields of a superclass can be accessed in a subclass ______.
by calling public or protected methods declared in the superclass.
For which of the following would polymorphism not provide a clean solution?
A program to compute a 5% savings account interest for a variety of clients.
Which of the following class members should usually be private?
Variables (or fields)
All of the following methods are implicitly final except ________.
a method in an abstract class
Interfaces can have ________ methods.
any number of
Every object in Java knows its own class and can access this information through method .
getClass
The UML distinguishes an interface from other classes by placing the word "interface" in above the interface name.
guillemets ' '
Which keyword is used to specify that a class will define the methods of an interface?
implements
The default implementation of method clone of Object performs a ________.
shallow copy
We may need to modify all the subclasses of the superclass if the superclass implementation changes. (T/F)
true
which of the following class members should usually be private?
variable (or fields)
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 -a method to refer implicitly to the instance variables and other methods of the object on which the method was called -an object to reference itself
Which of the following is not possible?
A class that inherits from two classes.
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 compilation error occurs.
Which statement best describes the relationship between superclass and subclass types?
A subclass reference can be assigned to a superclass variable, but a superclass reference cannot be assigned to a subclass variable.
All of the following methods are implicitly final except:
a method in an abstract class.
Which of the following could be used to declare abstract method method1 in abstract class Class1 (method1 returns an int and takes no arguments)?
public abstract int method1();
In Java SE 7 and earlier, an interface may contain ________.
public static final data and public abstract methods
Which method changes the text the label displays?
setText
A constructor cannot ________.
specify return types or return values
A final field should also be declared ________ if it is initialized in its declaration.
static
Which of the following keywords allows a subclass to access a superclass method even when the subclass has overridden the superclass method?
super
A subclass object can assign an invalid value to the superclass's instance variables, thus leaving an object in an inconsistent state. (T/F)
true
Abstract superclasses may contain data
true
Methods and instance variables can both be either public or private. (T/F)
true
Subclass methods are more likely to be written so that they depend on the superclass's data implementation. (T/F)
true
Which method returns an array of the enum's constants?
values
The default equals implementation of class Object determines ________.
whether two references refer to the same object in memory
Using the proceed keyword also gives a member _______.
package access
Using the protected keyword also gives a member ________.
package access
Superclass methods with this level of access cannot be called from subclasses.
private
Superclass methods with tis level of access cannot be called from subclasses
private
Polymorphism enables you to ________.
program in the general
Which interface is specifically intended to be implemented by classes that can be used with the try-with-resources statement?
AutoCloseable
Any concrete subclass that extends class Foo ________.
Both must implement a method called calculate and will not be able to access the instance variable a.
Using public set methods helps provide data integrity if ________.
Both the instance variables are private and the methods perform validity checking.
Objects are marked for garbage collection by method finalize. (T/F)
False
The static method ________ of class String returns a formatted String.
Format
When no access modifier is specified for a method or variable, the method or variable
Has package access
Composition is sometimes referred to as a(n) ________.
Has-a relationship
Class ________ represents an image that can be displayed on a JLabel.
ImageIcon
inheritance is sometimes referred to as a(n) ________.
Is-a relationship
Every class in Java, except ________, extends an existing class.
Object
Which of the following is not a superclass/subclass relationship?
Sailboat/Tugboat
Which interface is used to identify classes whose objects can be written to or read from some type of storage or transmitted across a network?
Serializable
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.
When a subclass constructor calls its superclass constructor, what happens if the superclass's constructor doesn't assign a value to an instance variable?
The program complies and runs because the instance variables are initialized to their default values.
A class that implements an interface but does not declare all of the interface's methods must be declared ________.
abstract
A(n) ________ class cannot be instantiated.
abstract
Which of the following statements about abstract superclasses is true?
abstract superclasses may contain data.
get methods are also commonly called ________ methods.
accessor
BigDecimal gives you control over how values are rounded. By default ________.
all calculations are exact and no rounding occurs
Which superclass members are inherited by all subclasses of that superclass?
protected instance variables and methods
An interface ________.
can be instantiated
Non-abstract classes are called ________.
concrete classes
Overriding a method differs from overloading a method because ________________.
override methods have the same signature
Polymorphism allows for specifics to be dealt with during ________.
execution
A static method can call instance methods directly.(T/F)
false
A superclass object is a subclass object.
false
Anonymous methods provide a shorthand notation for creating lambdas.
false
If the class you're inheriting from declares instance variables as private, the inherited class can access those instance variables directly.
false
It's OK to any of a class's methods from its constructors.
false
The BigDecimal method format receives a double argument and returns a BigDecimal object that represents the exact value specified. (t/f)
false
The compiler always creates a default constructor for a class. (T/F)
false
Use the access modifier package to give a method or variable package access. (T/F)
false
When you enhance an existing interface with default methods- any class that implemented the original interface will break.
false
With non-static interface methods, helper methods can now be declared directly in interfaces rather than in separate classes.
false
Classes and methods are declared final for all but the following reasons ________.
final methods are static
Which syntax imports all static members of class Math?
import static java.lang.Math.*.
When overriding a superclass method and calling the superclass version from the the subclass method, failure to prefix the superclass method name with they keyword super.() in the superclass method call causes
infinite recursion
To avoid duplicating code, use ___ rather than _____.
inheritance, the "copy-and-paste" approach
If the superclass contains only abstract method declarations, the superclass is used for ________.
interface inheritance
If the superclass contains only abstract method declarations, the super class is used for ______.
interface inheritance.
It is a UML convention to denote the name of an abstract class in ________.
italics
When a superclass variable refers to a subclass object and a method is called on that object, the proper implementation is determined at execution time. What is the process of determining the correct method to call?
late binding
Set methods are also commonly called ________ methods
mutator
An advantage of inheritance is that
objects of a subclass can be treated like objects of their superclass
An advantage of inheritance is that ________.
objects of a subclass can be treated like objects of their superclass