Unit 1

Question 1

Abstraction

Answer 1

Programming definition: “abstraction is the process of determining the set of features ( properties and methods) that a class will have”

Question 2

Fundamental concepts of objects

Answer 2

1) an object is some computer code that occupies space in memory
2) the object has two main parts
its properties(data)
and it’s methods(named blocks of code that do something when they are called)

Question 3

True or false: Everything in Java is an object.

Answer 3

False the eight primitive data types are not… they do not have any methods attached to them.

Question 4

define class in java

Answer 4

a collection of code that contains the instructions for building an object of that class in memory
aka the blueprint for creating an object

Question 5

When does an object get built in memory?

Answer 5

when the constructor method of the class file is called and executed

Question 6

class vs object analogy

Answer 6

follow the recipe (the class) for chocolate chip cookies and the objects are the cookies that come out of the oven.

Question 7

What are the three pillars of OOP?

Answer 7

1) Encapsulation
2) Inheritance
3) Polymorphism

Question 8

Basic concept of encapsulation:

Answer 8

Access to the data and methods of a class can be controlled using the visibility modifiers public, protected and private

Basic idea of encapsulation is about being able to control access to an object’s properties and methods.

Question 9

Inheritance

Answer 9

a sub-class (or child class) can inherit methods from its super class (or parent class) i.e it can make use of code written in the parent class without having that code written in its own class.
This means that we only need to write the method once in a parent or super class. (Yay! Less code to write!)
Sub-classes or child classes that are derived  or extended from the super class can inherit the method from the super class. Thus, they can call the method from the parent class.
In Java, every class we write inherits some methods and properties from the Object class, which Java provides for us. 
The Object class is often called “the mother of all classes”.

Question 10

Polymorphism aka late binding or dynamic binding

Answer 10

you can have several methods with the same name defined in different classes of a class hierarchy. This is called method over-riding, as opposed to method overloading. These are different concepts

If an object invokes a method, the actual method that runs depends on the class of the object that made the method call. The JVM determines  this while the program is running.
The JVM will ask “OK, what is the class of the object that just called this method?” When it determines that it was an object of, say, class MyWidget, then the JVM will run the method that is defined in the MyWidget class.

Question 11

Classes

Answer 11

a class file is used to describe entities that have similar properties or attributes. similar to data modeling done in DB work. A customer class would describe the attributes and methods of customer objects.

Question 12

In programing, think of a class as a ____ or ____ or ____ that defines the attributes and methods of objects of the same type. (T!)

Answer 12

description
blueprint
recipe

Question 13

Object: an object is a particular ____ of a class. (T!)

Answer 13

instance

Question 14

In java coding, we can think of an object as a collection of code that contains two things(T!):

Answer 14

1) some data in variables (aka properties, such as customer ID number)
2) some methods that can manipulate the data held in the variables.

Question 15

An object ____ both the data and the methods of the object in the block of memory assigned to hold the object. (T!)

Answer 15

holds

Analogy: a single chocolate chip cookie is an object of the ChocolateChipCookie class.

Question 16

The data held in an object is also sometimes referred to as the ____ of the object. (T!)

Answer 16

state

Question 17

The state of an object is represented by the _______

Answer 17

values held in it’s data variables.

Question 18

True or false: An objects state can change.

Answer 18

True if the variables values are modified.

Question 19

object’s methods are referred to as its (T!)

Answer 19

behavior.

Question 20

define behavior

Answer 20

The behavior of an object is defined by whatever methods have been declared in the class. It is what the object can do. (T!)

Question 21

Basic class diagram is a:

Answer 21

a rectangle separated vertically into three sections

top section holds the name of the class
middle section holds the attributes (data variables) and their data types
bottom section holds the methods associated with the class.

Question 22

T/F: Given a class diagram, you should be able to write the code that will define that class. (T!)

Answer 22

True

Question 23

public:

Answer 23

accessible from any class anywhere

Question 24

private:

Answer 24

no access from outside the class at all

Question 25

protected

Answer 25

accessible from any class in the same package OR from any class that is a sub class of the class. This sub class could be located in another package and still have the access rights

Question 26

if you don’t specify any access modifer on an attribute or a method, Java will use the DEFAULT level of visibility which means:

Answer 26

only classes in the same package will have access to the data members and methods. any classes in other packages WILL NOT have access, even if they are sub–classes derived from the class

Question 27

To declare an object reference variable, format is :

Answer 27

ClassName objectName;

Question 28

to instantiate an object we must use the ___ key word

Answer 28

new
objectName = new ClassName();

Question 29

objectName = new ClassName();the brackets indicate that you are actually calling a method here. What method is getting invoked?

Answer 29

a constructor method is being called

Question 30

a constructor method definition differs in 2 ways from all other methods in Java (T!)

Answer 30

1) constructor method name is always exactly the same as the class name (so it begins with an UPPER CASE letter according to standard naming convention)
2) no return type is ever specified for a constructor method (not even void). What does get returned from a constructor method is an object of that class, but we do not specify this in the method header.

Question 31

a default constructor is not defined by the programmer. It

Answer 31

it is provided by Java automatically (T!)

Question 32

Circle myCircle = new Circle( );

Answer 32

the constructor method that Java provides for us if we do not specifically write one into our class.(T!)

Question 33

method overloading

Answer 33

creating your own methods so that we can set the property values of an object at instantiation time by calling a particular constructor

Question 34

As soon as you define a constructor method

Answer 34

the java default constructor will no longer be available to us.

Question 35

True or False: a no arg constructor is the same as the default constructor provided by java

Answer 35

false they are different

Question 36

why don’t we have to instantiate an object of the class to use the method?

Answer 36

a static method

Question 37

true or false: A class method is defined using the static modifier.

Answer 37

T!rue 
•Means that you don’t have to create an object of the class in order to call the method.

Question 38

what scope does a static variable have?

Answer 38

a class scope
meaning it is visible to every method in the class

Question 39

true or false: Every object created from that class will have that variable and its value as part of its data

Answer 39

true

Question 40

true or false: there is just one copy of a class variable in memory

Answer 40

true

Question 41

where do we declare the class scope?

Answer 41

between the opening and closing brace of the class

Question 42

true or false: If the class variable value is changed, all the objects in existence get the change, because they all refer to it !

Answer 42

true

Question 43

a public variable can be accessed by any other class or object

Answer 43

true

Question 44

which type of modifier?
the variables and methods of the class can only be accessed inside the class, or used by objects of the same class.

Answer 44

private

Question 45

what is good practice generally when deciding which modifier to use

Answer 45

private

Question 46

default and protected modifiers are the same

Answer 46

default is more restrictive than the protected level(same as protected aka restricts visibility to classes in the same package but classes RELATED BY INHERITANCE that are OUTSIDE of the package are cut off.