Transcript 13X11
Java Lecture 1
CS 1311
Introduction
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Serious Stuff
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Put these in order
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Avoid damage to equipment and material
Get the job done
Avoid injuries
Maintain good community relations
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Normal World
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Avoid injuries
Avoid damage to equipment and material
Get the job done
Maintain good community relations
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Military@War
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Get the job done
Avoid injuries
Avoid damage to equipment and material
Maintain good community relations
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Ballistics
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Ballistics
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Ballistics
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vx
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Ballistics
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Ballistics
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Ballistics
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Ballistics
Assumptions
• Flat non-rotating earth
• Vacuum
• Constant gravity
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Ballistics Calculations
• Required rooms full of mathematicians
• Very slow, tedious work
• Anything that would help could help to win the war
• Money no object
• Commercialization not considered
• Software Engineering?
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Let's invent a computer
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Computer Programming
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Initially by hand
Big breakthrough: Machine translation
Analysis of computation
Church-Turing
Functional
Imperative/Procedural
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Paradigm Review
• Functional Programming
– Mathematical base
– Provably correct
– Disassociated from machine model
• Imperative/Procedural Programming
– Machine oriented
– Mathematical ties
• Object Oriented Programming
– Some features of both
– Result of industry maturation & growth
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Origins of OO
• USAF ATC Randolph AFB B220
Locations
Routines
Data
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Origins of OO
• USAF ATC Randolph AFB B220
• Simulation
Products
Conveyor
Workers
Machines
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Origins of OO
• USAF ATC Randolph AFB B220
• Simulation
• Large scale projects
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Origins of OO
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USAF ATC Randolph AFB B220
Simulation
Large scale projects
GUI's
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So what is it?
• A brief overview
• My favorite example
Queue
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Chez Guillaume
• Application to maintain 2 queues
• Allow adding to either list
• Allow removing from either list
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How might it be done?
head.tail
Restaurant Module
Enqueue Module
Data Structure
Dequeue Module
isEmpty Module
head.tail
Input Module
Output Module
Data Structure
Menu Module
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How might it be done?
head.tail
Restaurant Module
Enqueue Module
Data Structure
Dequeue Module
isEmpty Module
head.tail
Input Module
Output Module
Data Structure
Where is
the queue?
Menu Module
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The OO Approach
Queue Object
head.tail
Enqueue Module
Restaurant Object
Ref
Queue Object
head.tail
Dequeue Module
isEmpty Module
Enqueue Module
Input Module
Output Module
Menu Module
Dequeue Module
isEmpty Module
Data Object
Cust Data
Data Objects
Get Data Module
Set Data Module
The OO Approach
• Why do we want a new language?
• Why do we want to arrange things in such a
fashion?
• What are the goals?
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Goals
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Encapsulation
Reusability
Adaptability/Flexibility
Decentralization/Distribution
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OOP Terminology
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Abstract Data Type
Class
Object
Method
Fields/Attributes
References
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Characteristics of OOP Language
• Everything is an object
• A program is a bunch of objects telling each other
what to do by sending each other messages
• Each object has its own memory made up of other
objects
• Every object has a type which in OO terms means
that every object is an instance of some class
• All objects of a particular type can receive the
same messages. An object of type circle will also
be an object of type shape thus...
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Java
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Toasters
Smart cards
Killer apps
The wwweb
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Java, the good news
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Real
Very powerful
In demand
Software engineering
Universal
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Java, the bad news
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Real
Very powerful
Not an educational language
Jack of all trades/Master of none
Slow
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Clever Java Stuff
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Java program can be run by web browser
Borrowed a lot of syntax from c and c++
Give it away
WORA
Security
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Translation
• Compilation
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Fortran
Cobol
Pascal
Algol
C/C++
• Interpretation
– Basic
– Lisp
– Scheme
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Emulation
• How to sell a new computer to someone with lots
of software?
• Emulate the old hardware!
New Computer
Old
Software
Program
Emulating
Old Computer
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The Java Approach
• Compilation into ByteCode
Java
Source
Javac Compiler
Byte
Code
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The Java Approach
• Interpretation by the Java Virtual Machine
Any Computer
Byte
Code
Java
Virtual
Machine
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Why is this cool?
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The Internet
Java
Source
©Al Gore
Do this once
Javac Compiler
Byte
Code
Your Computer
Web Server
Your Favorite Browser
Java
Virtual
Machine
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Compilation/Execution
“Source
Code” [.java]
Java
compiler
Execute
program
Generic
“Byte Code” [.class]
OS-specific
JVM
interpreter
Need one of these
for every different
OS
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Sample Application
We create a file (using an editor) called “HelloWorld.java”
public class HelloWorld
{
public static void main(String argv[])
{
System.out.println(“Hello World!”);
}
}
We compile by typing (at the OS prompt):
javac HelloWorld.java
Hello World!
Which produces HelloWorld.class
Then we execute by typing:
java HelloWorld
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Demo
>javac HelloWorld.java
>java HelloWorld
Hello World!
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Quick Trix
• The name of the file must match the name of the
class EXACTLY!!!
• File: Bubba.java
Capitalization counts
• Contains:
class Bubba
{...
• Everything must be EXACTLY correct!!!
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A Final Word
• static
• static is a source of great confusion and
sometimes even frustration
• Here's the basic idea (don't worry if this is
confusing we'll explain it again
• and again
• and again
• and again
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Java Structure
• Java programs consist entirely of files containing
classes
• Classes are like blueprints or templates
• They describe the structure and operation of
objects.
• Objects are like whatever is made from a
blueprints or template.
• Objects are considered to be dynamic
• Sometimes there is a need for something to not
be dynamic hence you may declare it static.
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Questions?
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