Cs1002 - Object-Oriented Programming

Front 1

STATIC modifier

Back 1

Means that a member is associated with a class as a whole rather than just one instance; an individual object.

Front 2

Why use the 'this' keyword?

Back 2

To differentiate between a parameter and an attribute. I.e:

public void setSalary(int salary) {

this.salary = salary;

}

Front 3

What do modifiers control?

Back 3

-Visibility

-Mutability

-Association with class/object

Front 4

Explain DEFAULT FIELD VALUES.

Back 4

When an instance of an object is created, we must set that instance's field values to that of an attribute or another value; otherwise, the terminal will throw a nullpointException:main.

Front 5

Explain MAINTAINABILITY

Back 5

Any programmer must always be able to understand what the software is actually doing, so that they can easily make successful changes to the software. Maintainability is affected by readability, complexity and documentation.

Front 6

Explain READABILITY

Back 6

To make code have good readability, it is important to follow naming conventions, coding conventions and make the code neat, using automatic code from an IDE.

Front 7

Explain COMPLEXITY

Back 7

Code structure should be as simple and as logical as possible, but not necessarily the shortest it can be. Make a habit of using step-wise refinement wherein you break the code down into several simple steps to keep the flow of control as easy as possible.

Front 8

Explain DRY PRINCIPLE

Back 8

Don't repeat yourself; make sure to factor out shared code and use inheritance.

Front 9

Explain DOCUMENTATION

Back 9

The final product of a piece of code should include a user manual and a programmer guide; this can be constructed using comments to explain what the code is doing at a particular point.

Front 10

Difference between VALIDATION & VERIFICATION

Back 10

VALIDATION - does the product meet the requirements?

VERIFICATION - does the product work?

Front 11

Explain MODEL

Back 11

An abstract representation of something. It focuses on something's main features.

Front 12

What does UML stand for?

Back 12

UNIFIED MODELLING LANGUAGE

Front 13

Explain ENCAPSULATION

Back 13

The field values of an object cannot be directly seen by other classes, they can be accessed from the methods in the class that they are decalred; they control how field values are read and updated.

Front 14

Explain GETTERS

Back 14

A method in an class which returns the value held in a field.

Front 15

Explain SETTERS

Back 15

A method in a class which sets the content of a field to a certain value.

Front 16

Benefits of GETTERS AND SETTERS

Back 16

They provide standardised access to fields by other parts of your program and other programmers while using your code.

Front 17

Explain PUBLIC MODIFIER

Back 17

It means that the class, field,method or constructor can be accessed from anywhere.

NO restrictions.

Front 18

Explain PRIVATE MODIFIER

Back 18

It means that the class, field, method or constructor cannot be accessed from outside that class; field cannot be read or updated, method and constructor cannot be called.

Front 19

Explain PROTECTED MODIFIER

Back 19

It means that the class, field, method or constructor can only be accessed by the defining class, any class in the same package or any subclass of that class.

Front 20

Explain FINAL MODIFIER

Back 20

They are used to declare a field statement to be constant; a value that is declared public cannot be changed.

Front 21

Difference between VARIABLES & FIELDS

Back 21

FIELD - holds information relevant to objects of a specific class; defined in a class.

VARIABLE - holds temporary info to method execution; defined in a method.

Front 22

Explain CONSTRUCTORS

Back 22

It is like a special method that is executed whenever an instance, of the class it is defined in, is created. It will always initialise any new objects in the way you have specified within the constructor you are calling.

Front 23

Explain METHOD OVERLOADING

Back 23

When multiple methods are created which have the same identifier but different parameters.

Front 24

Explain INTERFACES

Back 24

They are contracts for how different parts of a piece of software may interact with one another. Each part can be implemented without knowing how other parts are implemented. An interface is a reference type in Java, it is similar to class, it is a collection of abstract methods. A class implements an interface, thereby inheriting the abstract methods of the interface.

Front 25

What can an interface contain?

Back 25

-constants

-method headers(name,parameters,return type)

-static methods

Front 26

How to structure an interface?

Back 26

public interface IPerson {

public void printDetails();

}

Front 27

Can you have instances of an interface?

Back 27

No, they merely describe the essentials of a class.

Front 28

What modifier is given to any method and constant declared in an interface?

Back 28

public, constants are declared as public, static and final.

Front 29

How do you create an interface and call it within another class?

Back 29

public interface Edible {

void.eat();

}

public static void myMethod(Edible e) {

e.eat();

}

Front 30

Benefits of INTERFACES

Back 30

Abstraction - can write code that uses objects without knowing exactly what class they belong to; just that they conform to some known interface. Easier to change one part of the program without changing others.

Can combing code with different people at different times.

Front 31

How to call an interface when creating a class?

Back 31

public class MyClass implements Interface1 {

}

Front 32

Can you have multiple interfaces?

Back 32

Yes

Front 33

Disadvantages of INTERFACES

Back 33

If two interfaces define a constant with the same identifier, there will be an error if you implement both and refer to the constant.

If two interfaces require the same method there isn't a problem, but if the only differ in return type then it is a problem.

Front 34

Explain INHERITANCE

Back 34

When information is common to several classes, we do not want to duplicate that information so we can have a subclass which inherits attributes and methods from another.

Front 35

Explain SUBCLASS

Back 35

The subclass is a class which inherits information from a superclass. I.e.

The subclass extends the superclass.

The subclass is a specialisation of the superclass.

Front 36

Explain SUPERCLASS

Back 36

The superclass passes down information to it's subclass(es). I.e.

The superclass is a generalisation of the subclass.

Front 37

Can a subclass inherit from more than one superclass?

Back 37

No

Front 38

Does a subclass inherit from all it's ancestors?

Back 38

Yes

Front 39

When is the SUPER keyword used?

Back 39

When calling upon a constructor which is in a superclass from the subclass; it allows for the subclass to do specific initialisation whereas the constructor in the super just initialises for info which may be common to a number of instances in it's subclasses.

Front 40

Explain ABSTRACT

Back 40

An abstract class cannot be instantiated; can be used as a place to define constants.

Front 41

Can abstract methods provide implementation?

Back 41

Yes

Front 42

What must you do if you are extending an abstract class?

Back 42

The programmer must implement all the methods declared in the abstract class.

Front 43

Difference between ABSTRACT CLASS & INTERFACE

Back 43

ABSTRACT CLASS - Can contain fields that are non-static and final, can contain implemented instance methods.

INTERFACE - Can contain static, final fields, method headers and static methods but can be implemented by multiple classes.

Front 44

Explain OVERRIDING

Back 44

The ability a subclass possesses wherein it can define it's own versions of methods inherited from a superclass; redefining the method is what is known as overriding. Parameters and return type must be the same, but implementation can be different.

Front 45

Can the SUPER keyword refer to a subclass?

Back 45

Yes, as long as it treats it like an instance of the superclass. I.e(Student extends Person):

This used in a student method means the current object is a student, but super used in a student method means current object is a person.

Front 46

Difference between OVERRIDING & OVERLOADING

Back 46

OVERLOADING - When multiple methods are defined in a class but with different parameters.

OVERRIDING - Redefining an inherited method in a subclass.

Front 47

Explain FINAL

Back 47

Final fields - cannot change their value.

Final classes - cannot be extended.

Final methods - cannot be overridden.

Front 48

Explain BYTE

Back 48

8 bit signed integer:

-128 to 127

Front 49

Explain SHORT

Back 49

16 bit signed integer:

-32768 to 32767

Front 50

Explain CHAR

Back 50

16 bit unsigned number:

0 to 65535

Front 51

Explain INT

Back 51

32 bit signed integer:

-2147483648 to 2147483647

Front 52

Difference between DOUBLE & FLOAT

Back 52

DOUBLE - 14 decimal places

FLOAT - 7 decimal places

Front 53

Explain TYPE COERCION

Back 53

Where java tries to make sense of incompatible types.

Front 54

Explain pseudo-code

Back 54

Informal high level description of the operating principle of the program.