CMSC OOPS MIDTERM

Object Oriented Programming

Programming by organizing data and code into objects; programming by using Object Oriented CS principles

Object

-Abstraction of a person, place, or thing

-Can know things, do things, or send messages to other objects or methods

Class

-Definition of a set of similar objects

-Template for defining and creating objects

-Name, list of attributes, list of methods

What makes a language an object oriented language?

-Provide support for classes

-Allow the creation of objects (instances of classes)

-Provide a mechanism for sending messages to objects

-Support OOP principles

OOP Principles

-Abstraction

-Encapsulation

-Inheritance

-Polymorphism

Computer Science Principle

Concept that has been shown over time that it can be applied in many areas of computer science as a part of a good solution

Abstraction

Representation of a real thing with something not real

-Real world: map

-CS: representing letters as numbers

Binding

Action of associating something with a specific item

-Real world: address to house, name to child

-CS: variable name to memory location, type with variable

Encapsulation

Hiding how something works

-Real world: car engine, computer

-CS: function that performs a service, creating an object that know things (and hiding how it does so)

Data Representation

Representing the information about real world data in a systemized way

-Real world: sheet music, braille

-CS: ASCII code, objects

Reuse

Using a particular technique, concept, or systems more than once

-Real world: legos

-CS: software libraries, methods of objects

Pattern

Template that can be used to solve problems

-Real world: dress pattern

-CS: system architecture patterns, patterns of arrangements of objects in an application

Polymorphism

Using same name to refer to similar functions in different classes of objects

-Real world: door handles / opening a door

-CS: methods with same names in different classes

Inhereitance

When parents pass on characteristics to children (reuse)

-Real world: children who look like parents

-CS: parent class passes on attributes and methods to child class

Separation of Concerns

Assigning responsibilities to the entity where they belong and not mixing the responsibilities between entities

-Real world: organizational responsibilities

-CS: separation into packages, method that does only one thing

UML

-Unified Modeling Language

-Notation for documentation of Object Oriented designs

UML Class Diagram Notation (Parts of Diagram)

-Name

-Attributes

-Methods

Associations UML

-Association: knows about, label, multiplicity ("0..*")

-Aggregation: "HAS A," parts are not deleted when the whole is deleted

-Composition: "IS A," parts are deleted when the whole is deleted

Inheritance UML

-"IS-A" relationship

-Generalization -\> specialization

-Parent -\> child

-Super class -\> sub class

Interface UML

-Specification of a group of methods that work together to do something

-Implement is a promise to implement the methods of the interface

Random Class

-java.util

Methods:

-Random()

-float nextFloat()

-int nextInt()

-int nextInt(int num)

Random Class Sample Code

Random generation \= new Random();

//number 1 - 10

int num \= generation.nextInt(10) + 1;

GUI Component

Object that defines a GUI element that displays on the screen and allows the user to interact with the system

Ex:

-Container

-Button

-Text Field

-Label

-Check Boxes

-Radio Buttons

-Menus

GUI Event

Object that represents some occurrence (user action) in which we may be interested

Ex:

-Key press

-Mouse click

-Mouse movement

GUI Listener

Object that waits for an event to occur and responds in some way when it does (written by developer)

Building a GUI

1. Add components for display

2. Write listeners and connect them to events

Swing Frame

-Container: can hold other components

-JFrame

Swing Panel

-Container: can hold other components