Programming Practice and Applications

Question 1

Class

Answer 1

a category or type of ‘thing’. Like a template or a blueprint.

Question 2

Object

Answer 2

Represents ‘things’ from the real world, or from some problem domain

Question 3

Methods

Answer 3

Methods can have parameters to pass additional information needed to execute. Can also return values

Question 4

Attributes

Answer 4

Characteristics of an object that is stored in a field

Question 5

A method signature

Answer 5

Made up of the method name and its parameters

Question 6

The state of an object

Answer 6

The set of values of all attributes defining an object

Question 7

Fields

Answer 7

Attributes, they store data persistently and define the state of an object. They are instance variables

Question 8

Structuring of a field

Answer 8

Always private, starts with a lowercase letter

Private datatype variable_name

Question 9

Constructor

Answer 9

Initialises an object

Question 10

Structure of a constructor

Answer 10

Always public, initial values stored in fields, can use parameters, same name as class

Question 11

Why are constructors public?

Answer 11

So they can be called by anyone who wants to use the class

Question 12

What are the two types of variables?

Answer 12

Instance variables and parameter variables which only exits while the parameter is being called, then gets called into a field

Question 13

What does a method do and what is it made up of

Answer 13

Methods implement the behaviour of an object. They are made up of a header and a body

Question 14

What is a mutator method?

Answer 14

They receive a parameter and they change an object. They have a void return type.

Question 15

What is an accessor method?

Answer 15

They have a non-void return value and they return a statement about the object.

Question 16

What is string concatenation?

Answer 16

Merging two or more strings

Question 17

What is a scope?

Answer 17

A scope is a textual block{ } in Java, which defines where the variable can be accessed

Question 18

What is a local variable?

Answer 18

A variable that only exists and are accessible within a specific scope. e.g when the method is called

Question 19

What is the scope and lifetime of a field?

Answer 19

It’s scope is the whole class and its lifetime is the lifetime of its object

Question 20

What is a lifetime?

Answer 20

Lifetime describes how long the variable can be used until it is destroyed

Question 21

What is abstraction?

Answer 21

The ability to ignore details of parts and focus on more important fundamental aspects

Question 22

What is modularisation?

Answer 22

The process of dividing a whole into well-defined parts which can be build and examined separately

Question 23

What is Constructor overloading?

Answer 23

Having more than one constructor

Question 24

What does the modulo operator do?

Answer 24

Returns the remainder of an integer divison

Question 25

What does null mean?

Answer 25

null means nothing has been assigned to the variable. Any primitive data type can be assigned to null.

Question 26

What are the primitive data types?

Answer 26

integer, boolean, floating point

Question 27

What is an external method call?

Answer 27

An object calling a method from a different class

Question 28

How do classes define types?

Answer 28

A class name can be used as a type for a variable. Objects can hold other objects or store references to them

Question 29

What is an object type?

Answer 29

Types defined by classes and strings, created manually

Question 30

What does 9+3+”cat” return?

Answer 30

“12cat”

Question 31

What does “cat”+9+3 return?

Answer 31

cat93

Question 32

What is a debugger?

Answer 32

Software that helps examine how an application executes and helps finds bugs.

Question 33

How to set a field with the same name as the parameter?

Answer 33

this.fieldName=parameter

Question 34

What Java Class libraries can we use for array?

Answer 34

import java.until.Arraylist

Question 35

What is a generic class type?

Answer 35

A collection that has one element type for all its elements

Question 36

How to declare an array list?

Answer 36

private ArrayList files;

Question 37

What is the diamond notation

Answer 37

If collection type is stated in the field declaration, you can leave it out in the constructor.

Question 38

Features of a collection

Answer 38

Increases its capacity as necessary, keeps a count, keeps elements in order

Question 39

what does filename.countains(“hi”) do?

Answer 39

Gives a partial match of the filename

Question 40

What are the ArrayList methods?

Answer 40

.add, .get, .remove, .size

Question 41

What types of loop is a for-each loop?

Answer 41

It is a definite loop because it goes through every element in a collection

Question 42

What type of loop is a while loop?

Answer 42

An indefinite loop because the amount of times it loops is unpredictable and dependent on whether the condition is met

Question 43

What are the benefits of a for-each loop?

Answer 43

It is easier to write, its safe because it is guaranteed to stop

Question 44

What are the benefits of a while loop?

Answer 44

We don’t have to process the whole collection doesn’t have to be used with a collection. Sadly it can cause an infinite loop

Question 45

How to check if two string are the same?

Answer 45

stringName.equals(“hi”) because String is a class in java and each string variable is a different object

Question 46

How to use the iterator object?

Answer 46

Iterator it = files.iterator();
while(it.hasNext()) {
ElementType tk= it.next();
.println(tk.getDetails());}

Question 47

How to use the iterator object to remove an element?

Answer 47

it.remove()

Question 48

When do we use iterator objects?

Answer 48

If we want to stop part way through a loop, it might be inefficient to go through indexed, when we want to remove an object from a collection