Week 2 Objects

Question 1

What do objects allow us to do?

Answer 1

Bring together variables and methods into a single thing

Question 2

What is the science of Java programming?

Answer 2

rules and syntax for making objects

Question 3

What is the art of Java programming?

Answer 3

Which variables and methods to bring together

Question 4

Scanner object - describe it

Answer 4

Has its own internal variable - stores it

Question 5

What is encapsulation?

Answer 5

use an object without understanding the underlying code

Question 6

What is java swing?

Answer 6

a package that helps you make a window

Question 7

Generally, what does a class have?

Answer 7

• a name (starting with a capital letter)
• some variables (class atttributes that belong to the class)
• some methods
• a constructor method that allows you to create a new object
• each class defined in its own file

Question 8

What does public mean?

Answer 8

it is a modifier that describes to which other objects they are visible.

All classes, class attributes and class methods have a modifier

public is visible by anything

Question 9

What does private mean?

Answer 9

these classes, attributes and methods can only be used by the class in which they are defined

i.e. can only be accessed within the class

Question 10

What does protected mean?

Answer 10

can be used only by other classes in the same package or that inherit from this class

Question 11

Are attributes private or public, generally speaking?

Answer 11

private

it maintains the integrity of the object - doesn’t allow other bits of the program to change the object in any way

Question 12

What are getter and setter methods?

Answer 12

they allow parts of the program to access and change attributes

you apply them to the variables

Question 13

this

Answer 13

use this in a class to refer to class attributes

e. g.
this. radius = radius;

When 2 attributes co-exist, if we don’t use this, the local one (the one passed to the method) is used

Question 14

What does static mean?

Answer 14

optional keyword, allows us to have class attributes and methods that can be accessed without creating an instance of the class i.e. an object

if not creating an object and influencing its methods, use static.. - static method as not doing anything to an object.

useful when we want to access methods without the overhead of making objects from that class

Question 15

What can be static?

Answer 15

attributes and methods!

*static attributes take the same value for all instances of a class and all objects made from that class e.g. pi = 3.14…

anytime we change the static variable, it changes it for all of them!

Question 16

What is a reference?

Answer 16

Person personOne = new Person(“Bill”, 56);

references store the address of the object they refer to

address of the object!

Question 17

What are the scope rules for objects?

Answer 17

Objects are available anywhere in our program (as long as there is a reference to that object in its scope)

1 Reference : 1 Object

Many References : 1 Object

Question 18

How can you tell if a new object has been created?

Answer 18

new

Question 19

How do we pass objects to methods?

Answer 19

via referencing

we tell the method the reference (address).

objects are visible everywhere as long as a reference is present

Question 20

What is the toString() method?

Answer 20

The toString() method returns the string representation of the object.

If you want to represent any object as a string