Java Chapter 6

Another term for an object of a class is _____

instance

An object is a(n) A. blueprint B. primitive data type C. variable D. instance of a class

instance of a class

Rectangle object fields

length and width

binding

matching a method call with the correct method- compiler uses the method signature to do this

public

member can be accessed by code inside the class or outside

private

member cannot be accessed by code outside the class, only by methods of the same class

method signature

method's name and data types of the method's parameters NOT the return type ex: add(int, int)

Class objects normally have __________ that perform useful operations on their data, but primitive variables do not.

methods

instance methods

methods that are not declared with a special keyword, static require an object to be created in order to be used

The process of matching a method call with the correct method is known as

binding

A class is analogous to a(n)

blueprint

A class's responsibilities are ______. a. the objects created from the class b. things the class knows c. actions the class performs d. both b and c

both b and c

After the header, the body of the method appears inside a set of _____.

braces {}

This is a method that is automatically called when an instance of a class is created.

constructor

This is automatically provided for a class if you do not write one yourself.

default constructor

no-arg constructor

does not accept arguments default constructor is a no-arg constructor

instance

each object that is created from a class

A class may not have more than one constructor. T or F

false

To find the classes needed for an object-oriented application, you identify all of the verbs in a description of the problem domain. T or F

false

when you write a constructor for a class, it still has the default constructor that Java automatically provides T or F

false

String class constructor shortcut

accepts a String literal as an argument, does not require new keyword --> String name="Michael";

This is a method that gets a value from a class's field, but does not change it.

accessor

accessor vs mutator

accessor: methods that retrieve data of fields mutator: methods that modify data of fields

This is a class member that holds data. a. method b. instance c. field d. constructor

field

A class specifies the ________ and ________ that a particular type of object has.

fields;methods

_____ represents an entity in the real world that can be distinctly identified.

an object

data hiding

an object hides its internal, private fields from code that is outside the class that the object is an instance of --> code outside the class must use the class's public methods to operate on an object's private fields

In a UML diagram to indicate the data type of a variable enter _____.

the variable name followed by a colon and the data type

Two or more methods in a class may have the same name, as long as this is different.

their parameter list

Each instance of a class has its own set of instance fields T or F

true

The new operator creates an instance of a class. T or F

true

method/constructor overloading

two or more methods/constructors can have the same name as long as their parameter lists are different

Rectangle box;

uninitialized local ref variable -must reference an object before it can be used --> box=new Rectangle(7,14);

stale data example

use a method to calculate area because if length or width are changed and the area does not then it is stale

default constructor

when an object is created its constructor is always called If you do not write one then Java provides one when the class is compiled sets everything to 0, false, or null

shadowing

a method may have a local variable with the same name as an instance field the local variable will hide the value of the instance field DISCOURAGED

constructor

a method that is automatically called when an object is created typically initialize instance fields and perform other object initialization

In UML diagrams, this symbol indicates that a member is private.

-

You use the _____ operator to access members of an object.

.

What is the value of times displayed? public class Test { public static void main(String[] args) { Count myCount = new Count(); int times = 0; for (int i=0; i<100; i++) increment(myCount, times); System.out.println("myCount.count = " + myCount.count); System.out.println("times = "+ times);} public static void increment(Count c, int times) { c.count++; times++;}} class Count { int count; Count(int c) { count = c;} Count() { count = 1;}}

0

What is the value of myCount.count displayed? public class Test { public static void main(String[] args) { Count myCount = new Count(); int times = 0; for (int i=0; i<100; i++) increment(myCount, times); System.out.println("myCount.count = " + myCount.count); System.out.println("times = "+ times);} public static void increment(Count c, int times) { c.count++; times++;}} class Count { int count; Count(int c) { count = c;} Count() { count = 1;}}

101

Suppose you declare Date d. d is now called _____ A. a variable that holds an integer value B. a reference variable for an object C. an object D. an object value

B. a reference variable for an objec

The default value for data field of a boolean type, numeric type, object type is _____, respectively. A. true, 1, Null B. false, 0, null C. true, 0, null D. true, 1, null

B. false, 0, null

Suppose you wish to provide an accessor method for a boolean property finished, what signature of the method should be? A. public void getFinished() B. public boolean getFinished() C. public boolean isFinished() D. public void isFinished()

C. public boolean isFinished()

Given the declaration Circle x = new Circle(), which of the following statement is most accurate? A. x contains an int value. B. x contains an object of the Circle type. C. x contains a reference to a Circle object. D. You can assign an int value to x.

C. x contains a reference to a Circle object.

Given the declaration Circle[] x = new Circle[10], which of the following statement is most accurate? A. x contains an array of ten int values. B. x contains an array of ten objects of the Circle type. C. x contains a reference to an array and each element in the array can hold a reference to a Circle object. D. x contains a reference to an array and each element in the array can hold a Circle object.

C. x contains a reference to an array and each element in the array can hold a reference to a Circle object

A UML diagram does not contain _____. A. the class name B. the method names C. the field names D. object names

D. object names

What does the following UML diagram entry mean? + setHeight(h : double) : void A. this is a public attribute named Height and is a double data type B. this is a private method with no parameters and returns a double data type C. this is a private attribute named Height and is a double data type D. this is a public method with a parameter of data type double and does not return a value

D. this is a public method with a parameter of data type double and does not return a value

Data hiding, which means that critical data stored inside the object is protected from code outside the object is accomplished in Java by _____. A. using the public access specifier on the class methods B. using the private access specifier on the class methods C. using the private access specifier on the class definition D. using the private access specifier on the class fields

D. using the private access specifier on the class fields

You can always use the default constructor even though the non-default constructors are defined in the class. T or F

False

access specifier

Java keyword that indicates how a field or method can be accessed public or private

2 general capabilities of objects

can store data in fields can perform operations called methods

A collection of programming statements that specify the fields and methods that a particular type of object may have

class

Variables that are shared by every instances of a class are _____.

class variables

definition of a class

code that describes a particular type of object specifies the data an object can hold (fields) and actions an object can perform (methods) blueprint to create an object

special properties of constructors

have the same name as the class have no return type may not return any values typically public

this is a method that stores a value in a field or in some other way changes the value of a field

mutator

this key word causes an object to be created in memory

new

Rectangle object methods

setLength setWidth getLength getWidth getArea

When a local variable has the same name as a field, the local variable's name does this to the field's name.

shadows

when the value of an item is dependent on other data, and that item i not updated when the other data is changed, what has the value become?

stale