OOP terms

Question 1

what are the attributes of the object

Answer 1

its state eg colour, age,, size

Question 2

what is the behaviour of the object

Answer 2

its functionality eg walk, sing

Question 3

what is a class

Answer 3

a blueprint for a custom type

Question 4

what does UML stand for

Answer 4

unified modeling language

Question 5

what does + mean inUML

Answer 5

Public

Question 6

what does - mean in UML

Answer 6

Private

Question 7

create an object of class student

Answer 7

Student studentName = new Student();

Question 8

what does encapsulate mean

Answer 8

not allow it to be exposed to the world

Question 9

when are getters and setters used

Answer 9

when variables are private

Question 10

why do we use getters and setters rather than leaving variables public

Answer 10

so that they cant be changed to crap eg length being a minus number

Question 11

what is stack memory used for

Answer 11

variables and function calls

Question 12

what is heap memory used for

Answer 12

to store objects

Question 13

formal name for getters and setters

Answer 13

instance methods

accessors and mutators

Question 14

creating an array of objects

Answer 14

type(class name) arrayName = new type[x]

Question 15

what is method overloading

Answer 15

when there are more than one method with the same name but the compiler can tell them apart by their parameters/ list of parameters

Question 16

why might static variables be used

Answer 16

universal to everyone

Question 17

how are static variables accessed

Answer 17

ClassName.VariableName

Question 18

can static variables be accessed outside of the class without creating an pbject of that class

Answer 18

yes

Question 19

where are static variables stored

Answer 19

stack

Question 20

what is a java interface

Answer 20

the minimum methods that must be implemented for the object to be useful

Question 21

example of making a class that uses an interface

Answer 21

public class Rectangle implements Shape

Question 22

what is a constructor

Answer 22

a method which initialises an object

Question 23

when are constructors invoked

Answer 23

object creation

Question 24

if you don’t make a constructor what happens

Answer 24

java makes a deafult one for you, all attributes set to 0 or null

Question 25

does constructor have a return type

Answer 25

no

Question 26

what should constructor be called

Answer 26

same name as class

Question 27

what is a constructor which takes in parameters called

Answer 27

parametrized constructor

Question 28

what is constructor overloading

Answer 28

multiple constructors, each with different parameter lists needed to handle different cases

Question 29

what does key word this refer to

Answer 29

current object

Question 30

what is constructor chaining

Answer 30

reusing constructors from other classes

Question 31

when using constructor chaining, in what psoition should the call to the constructor be in the method

Answer 31

first statement

Question 32

what is inheritence

Answer 32

a new class is created using an existing classes methods, possibly adding more capabilities

Question 33

benefits of inheritence

Answer 33

more efficient
cheaper
loss copying

Question 34

in inheritance what is the parent class called

Answer 34

superclass

Question 35

in inheritence what is the child class called

Answer 35

subclass

Question 36

what is a direct subclass

Answer 36

inherits explicitly from superclass above

Question 37

what is an indirect subclass

Answer 37

inherits from classes above the class above

Question 38

in java, all classes have the superclass of what

Answer 38

Object

Question 39

can you inherit from multiple classes into one class

Answer 39

no

Question 40

are constructors inherited

Answer 40

no, must be called using super

Question 41

methods inherited from the superclass must be….

Answer 41

overrided

Question 42

how can superclass methods be accessed in a subclasss

Answer 42

using super.methodName( )

Question 43

what is polymorphism

Answer 43

when many objects can be passed into the same method and at runtime, the program is able to establish which versions to use

(late binding)

Question 44

what is upcasting

Answer 44

the typecasting of a child object to a parent object

Question 45

what is an abstract class

Answer 45

a superclass from which other classes inherit and so they all have a common design

but none of its methods are functioning, so it cannot be used to instantiate objects

similar to an interface

Question 46

what are concrete classes

Answer 46

classes which can be used to instantiate objects

Question 47

a class which contains abstract methods must be a

Answer 47

n abstract class