OOP

Question 1

class

Answer 1

template of blueprint from which objects are created and receive their states(properties/fields) and behaviour(methods)

Question 2

static

Answer 2

class method
belongs to class
don’t need an instance to use it
underline

Question 3

non static

Answer 3

instance method
belongs to object
need that instance to call it

Question 4

void

Answer 4

method doesn’t return anything

Question 5

object

Answer 5

an instance of a class
there can be multiple instances of a class in a program.
contains both the data and the function, which operates on the data.
has its own unique properties(data) and each method can be called on each object.

Question 6

abstraction

Answer 6

displaying only essential information and hiding the details.

creating new data types suited for a specific application (that the programming language does not know about.)

Question 7

encapsulation

Answer 7

hiding the code and data into a single unit to protect the inner workings of an object (concealing the implementation of the object)

makes use of information hiding (make properties private - use methods to access them.)

Question 8

information hiding

Answer 8

inner workings of a class being hidden from the class user

use access modifier private (in order to have encapsulation)

Question 9

difference between abstraction and encapsulation

Answer 9

Abstraction hides details at the design level (complexity) , while Encapsulation hides details at the implementation level (inner workings).

Question 10

public

Answer 10

Accessible everywhere
can be accessed by the class.it is declared in and by by any other class
+

Question 11

private

Answer 11

-
Accessible only in its own class

Question 12

protected

Answer 12

Accessible by class and any subclass (in any package) and by any other class in the same package

Question 13

inheritance

Answer 13

one object acquires the properties and behaviours of the parent object (along w having their own unique attributes)

key word- extends use clear arrow

parent- child relationship between superclass + subclass

suitable when 2 classes have many fields + methods in common

Question 14

default constructor

Answer 14

constructor w/ no parameters
sets attributes of the object to default values

Question 15

polymorphism

Answer 15

ability of an object or method to take on multiple forms based on its current situation
overriding + overloading

Question 16

variables

Answer 16

describes the fields/Attributes/Characteristics/Properties of the object

store data for processing.

given a name (identifier), are of a specific type and have a value assigned to it.

all take up a different amount of size + has a unique address

Question 17

local variables

Answer 17

declared inside methods
do not exist when method is finished, cannot be used outside of method
used instead of global- space in RAM not wasted
Different methods can have local variables with the same names because the methods cannot see
each other’s local variables.

Question 18

global variables

Answer 18

declared in class above all methods
scope is inside the entire program
can be used by all methods

Question 19

access modifiers

Answer 19

used to tell which code has access to certain fields and methods

Question 20

types of variables

Answer 20

primitive- cant invoke methods
reference/class type.-has methods

Question 21

types of variables

Answer 21

primitive- cant invoke methods
reference/class type.-has methods

Question 22

constructor

Answer 22

special method in class called when an object is instantiated
purpose- initialise class fields

Question 23

accessor method

Answer 23

get method
have a specific data type/ return type
returns a field value
allows for visibility of data - other classes will have access to the values
no parameters

Question 24

mutator method

Answer 24

set method
modify field values
void
other classes can edit data of object
has parameters

Question 25

typed methods

Answer 25

return a value

Question 26

void methods

Answer 26

don’t return a value

Question 27

helper methods

Answer 27

declared as private
solve some problem in the class
called by public methods in the class

Question 28

instantiation

Answer 28

act of creating an object from the class

Question 29

scope of variable

Answer 29

defines where variable can be used in a programme and its lifetime
depends on where it is declared in the program
local or global

Question 30

method overloading

Answer 30

creation of multiple methods in a single class with the same name but with different method signature (parameters/data types )
—method signature changes
-done innone class
can overload static,final or private method
-bonded by static binding at compile time

Question 31

method overriding

Answer 31

child class uses method created in parent class (same name)

@override

-method signature remains the same
-only done in subclass
-cannot override static,final + private method
-subject to dynamic binding at run time (check which method to use )

Question 32

method resolution

Answer 32

When you have methods that have been overloaded, Java needs to figure out which method to call based on the parameters given when the method is called.

Question 33

constants

Answer 33

cannot be assigned another value later in the programme
public static final NAME

Question 34

formal vs actual parameters

Answer 34

actual- when you call a method and pass real values in it
formal-when you create a method and pass values as parameters

Question 35

method signature

Answer 35

first line that describes whether or not the method is typed or void, what its name is, what parameters it contains,

modifier,return type,name,parameters

Question 36

reasons protected access does not offer secure protection

Answer 36

1. Anyone can create a subclass from an
   existing class and could therefore access and change values in fields which could have dire consequences on applications using those classes.
2. In Java, all classes in the same package have access to protected fields, whether or not they are subclasses.

Question 37

default access

Answer 37

nothing specified

Accessible by any class or subclass in the same package. This is sometimes called package accessibility

Question 38

array

Answer 38

data structure
collection of variables of same type
elements ordered + each has a specific + constant position (index)

Question 39

method

Answer 39

collection of statements that are grouped together to perform an operation
defines behaviour

Question 40

toString method

Answer 40

create String representation of an object.
every class has default toString method

Question 41

for loops

Answer 41

allows you to efficiently write a loop that needs to execute the same code a specific number of times.
for (initialisation,condition,change) { action}

Question 42

while loops

Answer 42

repeatedly executes a target statement as long as a given condition is true.
initialisation
while (condition is true) { action
change}

Question 43

advantages of inheritance

Answer 43

Reusability of code: we can use our existing code in our subclass from the super class
• Subclasses can take on existing functionality while creating their unique methods for their access only
• information hiding

Question 44

advantages of encapsulation

Answer 44

guarantees integrity of an object’s data as it is securely hidden
restricted data access from outside sources

Question 45

call method from parent class (override)

Answer 45

super.methodName()

for constructor - super(field,field)

Question 46

composition

Answer 46

The has-a relationship between two Java objects. One object is a field of another object.