007 - Classes and Objects

Question 1

In a class declaration. The __________ (the area between the braces) contains all the code that provides for the life cycle of the objects created from the class:

Answer 1

class body

Question 2

The class body contains: 
A. \_\_\_\_\_\_\_\_\_\_ for initializing new objects
B. \_\_\_\_\_\_\_\_\_\_ for the fields that provide the state of the class and its objects
C. \_\_\_\_\_\_\_\_\_\_ to implement the behavior of the class and its objects.

Answer 2

constructors

declarations

methods

Question 3

class declarations can include these components, in order:

1. _________ such as public, private.
2. _________, with the initial letter capitalized.
3. __________ preceded by the keyword extends.
4. _________ preceded by the keyword implements.
5. __________, surrounded by braces, {}.

Answer 3

1. Modifiers
2. The class name
3. the class’s parent (superclass), if any. (A class can only extend (subclass) one parent.)
4. A comma-separated list of interfaces implemented by the class, if any (A class can implement more than one interface.)
5. The class body

Question 4

There are several kinds of variables:

1. Member variables in a class: __________.
2. Variables in a method or block of code: __________.
3. Variables in method declarations: __________.

Answer 4

fields

local variables

parameters

Question 5

Field declarations are composed of three components, in order:

1. __________, such as public or private.
2. The field’s __________.
3. The field’s __________.

Answer 5

1. Zero or more modifiers
2. type
3. name

Question 6

__________ used lets you control what other classes have access to a member field.

Answer 6

The first (left-most) modifier

Question 7

__________—the field is accessible from all classes.

Answer 7

public modifier

Question 8

__________ —the field is accessible only within its own class.

Answer 8

private modifier

Question 9

In the spirit of encapsulation, it is common to make fields __________.

Answer 9

private

Question 10

All variables must have a __________.
You can use __________ such as int, float, boolean, etc.

Or you can use __________, such as strings, arrays, or objects.

Answer 10

type

primitive types

reference types

Question 11

the same naming rules and conventions are used for method and class names, except that

the first letter of a class name \_\_\_\_\_\_\_\_\_\_, 
the first (or only) word in a method name \_\_\_\_\_\_\_\_\_\_.

Answer 11

should be capitalized

should be a verb

Question 12

The only required elements of a method declaration are:
the method's \_\_\_\_\_\_\_\_\_\_, 
the method's \_\_\_\_\_\_\_\_\_\_,
a pair of \_\_\_\_\_\_\_\_\_\_, 
and a \_\_\_\_\_\_\_\_\_\_.

Answer 12

return type
name
parentheses, ()
body between braces, {}

Question 13

More generally, method declarations have six components, in order:

1__________such as public, private.

2. __________ the data type of the value returned by the method, or void.
3. __________ the rules for fields apply to methods as well, convention is a little different.
4. __________ in parenthesis.
5. __________ to be discussed later.
6. __________, enclosed between braces.

Answer 13

1. Modifiers
2. The return type
3. The method name
4. The parameter list: a comma-delimited list of input parameters, preceded by their data types, enclosed by parentheses, (). If there are no parameters, you must use empty parentheses.
5. An exception list
6. The method body: the method’s code, including the declaration of local variables, goes here.

Question 14

Two of the components of a method declaration comprise the method signature: __________ and __________.

Answer 14

the method’s name

the parameter types

Question 15

Definition: Two of the components of a method declaration comprise __________: the method’s name and the parameter types.

Answer 15

the method signature

Question 16

By convention, method names should be __________ or __________, followed by adjectives, nouns, etc.
In multi-word names, the first letter of each of the second and following words __________.

Answer 16

a verb in lowercase or a
multi-word name that begins with a verb in lowercase

should be capitalized

Question 17

Typically, a method has a unique name within its class. However, a method might have the same name as other methods due to __________.

Answer 17

method overloading

Question 18

Java can distinguish between methods with different __________.

Answer 18

method signatures

Question 19

__________ means that methods within a class can have the same name if they have different parameter lists

Answer 19

Method overloading

Question 20

Overloaded methods are differentiated by the __________ and the __________ of the __________ passed into the method.

Answer 20

The number and the type of the arguments

Question 21

You cannot declare more than one method with the same name and the same number and type of arguments, because __________.

Answer 21

the compiler cannot tell them apart

Question 22

__________, so you cannot declare two methods with the same signature even if they have a different return type.

Answer 22

The compiler does not consider return type when differentiating methods

Question 23

__________ should be used sparingly, as they can make code much less readable.

Answer 23

Overloaded methods

Question 24

Constructor declarations look like method declarations—except that __________ and __________.

Answer 24

they use the name of the class and have no return type

Question 25

To create a new Bicycle object called myBike, __________ is called by __________

Answer 25

a constructor

the new operator

Bicycle myBike = new Bicycle(30, 0, 8);

Question 26

new Bicycle(30, 0, 8)

creates __________ for the object and initializes __________.

Answer 26

space in memory

its fields

Question 27

As with methods, the Java platform differentiates __________ on the basis of the number of arguments in the list and their types.

Answer 27

constructors

Question 28

You cannot write two constructors that have the same number and type of arguments for the same class, because the platform would not be able to tell them apart. Doing so causes a __________.

Answer 28

compile-time error

Question 29

You don’t have to provide any constructors for your class, but you must be careful when doing this. The compiler automatically __________ for any class without constructors.

Answer 29

provides a no-argument, default constructor

Question 30

If your class has no explicit superclass, then it has an __________, which does have a no-argument constructor.

Answer 30

implicit superclass of Object

Question 31

You can use __________in a constructor’s declaration to control which other classes can call the constructor.

Answer 31

access modifiers

Question 32

__________ refers to the ilist of variables in a method declaration. __________ are the actual values that are passed in when the method is _________.

Answer 32

Parameters

Arguments

invoked

Question 33

You can use a construct called __________ to pass an arbitrary number of values to a method. You use it when you don’t know how many of a particular type of argument will be passed to the method.

Answer 33

varargs

Question 34

__________ is a shortcut to creating an array manually.

Answer 34

varargs

Question 35

To use varargs, you follow the type of the last parameter by __________ then a space, and __________. The method can then be called with any number of that parameter, including __________.

Answer 35

an ellipsis (three dots, …),

the parameter name

none

Question 36

You will most commonly see varargs with __________.

Answer 36

the printing methods;
for example, this printf method:

public PrintStream printf(String format, Object… args)

allows you to print an arbitrary number of objects. It can be called like this:

System.out.printf(“%s: %d, %s%n”, name, idnum, address);
or like this

System.out.printf(“%s: %d, %s, %s, %s%n”, name, idnum, address, phone, email);

Question 37

The __________ of a parameter must be unique in its scope. It cannot be __________ for the same method or constructor, and it cannot be __________ of a local variable within the method or constructor.

Answer 37

name

the same as the name of another parameter

the name

Question 38

A parameter can have the same name as one of the class’s fields. If this is the case, the parameter is said to __________ the field.

Answer 38

shadow

Question 39

__________ can make your code difficult to read and is conventionally used only within constructors and methods that set a particular field.

Answer 39

Shadowing fields

Question 40

Primitive arguments, such as an int or a double, are passed into methods __________. This means that any changes to the values of the parameters exist only within the scope of the method. When the method returns, the parameters __________ and any changes to them __________.

Answer 40

by value

are gone

are lost

Question 41

Reference data type parameters, such as objects, are also passed into methods __________. This means that when the method returns, the passed-in reference __________ However, the values of the object’s fields __________ in the method, if they have __________.

Answer 41

by value

still references the same object as before.

can be changed in the method, if they have the proper access level.

Question 42

An object creation statement can have three parts:

1. __________: associate a variable name with an object type.
2. __________: The new keyword is a Java operator that creates the object.
3. _________: The new operator is followed by a call to a constructor, which initializes the new object.

Answer 42

1. Declaration
2. Instantiation
3. Initialization

Question 43

Simply declaring a reference variable __________ For that, you need to use the __________.

Answer 43

does not create an object.

new operator

Question 44

The new operator __________ by allocating memory for a new object and returning a reference to that memory. The new operator also invokes __________.

Answer 44

instantiates a class

the object constructor

Question 45

The phrase “instantiating a class” means the same thing as “_________”

Answer 45

creating an object.

Question 46

The new operator requires a single, postfix argument: a call to a _________.

Answer 46

constructor