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Presentation slides for |
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Java Software Solutions |
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Foundations of Program Design |
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Third Edition |
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by John Lewis and William Loftus |
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Java Software Solutions is published by
Addison-Wesley |
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Presentation slides are copyright 2002 by John
Lewis and William Loftus. All rights reserved. |
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Instructors using the textbook may use and
modify these slides for pedagogical purposes. |
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Object-Oriented Software Development |
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problem solving |
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program design, implementation, and testing |
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object-oriented concepts |
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classes |
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objects |
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interfaces |
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inheritance |
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polymorphism |
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graphics and Graphical User Interfaces |
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the Java programming language |
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We first need to explore the fundamentals of
computer processing |
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Chapter 1 focuses on: |
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components of a computer |
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how those components interact |
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how computers store and manipulate information |
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computer networks |
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the Internet and the World Wide Web |
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programming and programming languages |
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graphic systems |
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Hardware |
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the physical, tangible parts of a computer |
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keyboard, monitor, disks, wires, chips, etc. |
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Software |
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programs and data |
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a program is a series of instructions |
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A computer requires both hardware and software |
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Each is essentially useless without the other |
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Operating System |
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controls all machine activities |
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provides the user interface to the computer |
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manages resources such as the CPU and memory |
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Windows XP, Windows 2000, Unix, Linux, Mac OS |
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Application program |
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generic term for any other kind of software |
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word processors, missile control systems, games |
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Most operating systems and application programs
have a graphical user interface (GUI) |
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There are two basic ways to store and manage
data: |
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Analog |
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continuous, in direct proportion to the data
represented |
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music on a record album - a needle rides on
ridges in the grooves that are directly proportional to the voltages sent
to the speaker |
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Digital |
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the information is broken down into pieces, and
each piece is represented separately |
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music on a compact disc - the disc stores
numbers representing specific voltage levels sampled at specific times |
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Computers store all information digitally: |
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numbers |
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text |
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graphics and images |
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video |
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audio |
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program instructions |
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In some way, all information is digitized -
broken down into pieces and represented as numbers |
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For example, every character is stored as a
number, including spaces, digits, and punctuation |
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Corresponding upper and lower case letters are
separate characters |
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Once information is digitized, it is represented
and stored in memory using the binary number system |
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A single binary digit (0 or 1) is called a bit |
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Devices that store and move information are
cheaper and more reliable if they have to represent only two states |
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A single bit can represent two possible states,
like a light bulb that is either on (1) or off (0) |
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Permutations of bits are used to store values |
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Each permutation can represent a particular item |
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There are 2N permutations of N bits |
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Therefore, N bits are needed to represent 2N
unique items |
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Consider the following specification for a
personal computer: |
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950 MHz Pentium 4 Processor |
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512 MB RAM |
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30 GB Hard Disk |
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CD-RW 24x / 10x / 40x |
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17” Video Display with 1280 x 1024 resolution |
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56 Kb/s Modem |
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What does it all mean? |
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Every memory device has a storage capacity,
indicating the number of bytes it can hold |
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Capacities are expressed in various units: |
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Main memory is volatile -
stored information is lost if the electric power is removed |
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Secondary memory devices are nonvolatile |
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Main memory and disks are direct access devices
- information can be reached directly |
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The terms direct access and random access often
are used interchangeably |
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A magnetic tape is a sequential access device
since its data is arranged in a linear order - you must get by the
intervening data in order to access other information |
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RAM
- Random Access Memory
(direct access) |
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ROM
- Read-Only Memory |
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The terms RAM and main memory are basically
interchangeable |
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ROM could be a set of memory chips, or a
separate device, such as a CD ROM |
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Both RAM and ROM are random (direct) access
devices! |
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RAM probably should be called Read-Write Memory |
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A CD-ROM is portable read-only memory |
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A microscopic pit on a CD represents a binary 1
and a smooth area represents a binary 0 |
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A low-intensity laser reflects strongly from a
smooth area and weakly from a pit |
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A CD-Recordable (CD-R) drive can be used to
write information to a CD once |
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A CD-Rewritable (CD-RW) can be erased and reused |
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The speed of a CD drive describes how fast it
can write information to a CD-R (24x), a CD-RW (10x), and how fast it can
read (40x) |
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A DVD is the same size as a CD, but can store
much more information |
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The format of a DVD stores more bits per square
inch |
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A CD can store 650 MB, while a standard DVD can
store 4.7 GB |
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A double sided DVD can store 9.4 GB |
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Other advanced techniques can bring the capacity
up to 17.0 GB |
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There are various recordable DVD technologies –
the market will determine which will dominate |
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A CPU is on a chip called a microprocessor |
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It continuously follows the fetch-decode-execute
cycle: |
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The speed of a CPU is controlled by the system
clock |
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The system clock generates an electronic pulse
at regular intervals |
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The pulses coordinate the activities of the CPU |
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The speed is measured in megahertz (MHz) |
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The size of a monitor (17") is measured
diagonally, like a television screen |
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Most monitors these days have multimedia
capabilities: text, graphics,
video, etc. |
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A monitor has a certain maximum resolution ,
indicating the number of picture elements, called pixels, that it can
display (such as 1280 by 1024) |
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High resolution (more pixels) produces sharper
pictures |
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Data transfer devices allow information to be
sent and received between computers |
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Many computers include a modulator-demodulator
or modem, which allows information to be moved across a telephone line |
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A data transfer device has a maximum data
transfer rate |
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A modem, for instance, may have a data transfer
rate of 56,000 bits per second (bps) |
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A network is two or more computers that are
connected so that data and resources can be shared |
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Most computers are connected to some kind of
network |
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Each computer has its own network address, which
uniquely identifies it among the others |
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A file server is a network computer dedicated to
storing programs and data that are shared among network users |
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Each computer in a network could be directly
connected to every other computer in the network |
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These are called point-to-point connections |
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Most networks share a single communication line |
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Adding a new computer to the network is
relatively easy |
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The Internet is a WAN which spans the entire
planet |
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The word Internet comes from the term internetworking,
which implies communication among networks |
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It started as a United States government
project, sponsored by the Advanced Research Projects Agency (ARPA) -
originally it was called the ARPANET |
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The Internet grew quickly throughout the 1980s
and 90s |
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Less than 600 computers were connected to the
Internet in 1983; by the year 2000
there were over 10 million |
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A protocol is a set of rules that determine how
things communicate with each other |
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The software which manages Internet
communication follows a suite of protocols called TCP/IP |
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The Internet Protocol (IP) determines the format
of the information as it is transferred |
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The Transmission Control Protocol (TCP) dictates
how messages are reassembled and handles lost information |
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Each computer on the Internet has a unique IP
address, such as: |
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204.192.116.2 |
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Most computers also have a unique Internet name,
which also is referred to as an Internet address: |
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spencer.villanova.edu |
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kant.gestalt-llc.com |
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The first part indicates a particular computer (spencer) |
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The rest is the domain name, indicating the
organization (villanova.edu) |
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The last part of each domain name, called a top-level
domain (TLD) indicates the type of organization: |
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A domain name can have several parts |
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Unique domain names mean that multiple sites can
have individual computers with the same local name |
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When used, an Internet address is translated to
an IP address by software called the Domain Name System (DNS) |
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There is no one-to-one correspondence between
the sections of an IP address and the sections of an Internet address |
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The World Wide Web allows many different types
of information to be accessed using a common interface |
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A browser is a program which accesses and
presents information |
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text, graphics, video, sound, audio, executable
programs |
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A Web document usually contains links to other
Web documents, creating a hypermedia environment |
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The term Web comes from the fact that
information is not organized in a linear fashion |
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Web documents are often defined using the HyperText
Markup Language (HTML) |
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Information on the Web is found using a Uniform
Resource Locator (URL): |
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http://www.lycos.com |
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http://www.villanova.edu/webinfo/domains.html |
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ftp://java.sun.com/applets/animation.zip |
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A URL indicates a protocol (http), a domain, and
possibly specific documents |
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The purpose of writing a program is to solve a
problem |
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The general steps in problem solving are: |
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Understand the problem |
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Dissect the problem into manageable pieces |
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Design a solution |
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Consider alternatives to the solution and refine
it |
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Implement the solution |
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Test the solution and fix any problems that
exist |
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Many software projects fail because the
developer didn't really understand the problem to be solved |
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We must avoid assumptions and clarify
ambiguities |
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As problems and their solutions become larger,
we must organize our development into manageable pieces |
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This technique is fundamental to software
development |
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We will dissect our solutions into pieces called
classes and objects, taking an object-oriented approach |
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A programming language specifies the words and
symbols that we can use to write a program |
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A programming language employs a set of rules
that dictate how the words and symbols can be put together to form valid program
statements |
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The Java programming language was created by Sun
Microsystems, Inc. |
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It was introduced in 1995 and it's popularity
has grown quickly since |
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It is an object-oriented language |
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In the Java programming language: |
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A program is made up of one or more classes |
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A class contains one or more methods |
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A method contains program statements |
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These terms will be explored in detail
throughout the course |
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A Java application always contains a method
called main |
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See Lincoln.java (page 30) |
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Comments in a program are called inline
documentation |
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They should be included to explain the purpose
of the program and describe processing steps |
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They do not affect how a program works |
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Java comments can take three forms: |
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Identifiers are the words a programmer uses in a
program |
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An identifier can be made up of letters, digits,
the underscore character ( _ ), and the dollar sign |
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Identifiers cannot begin with a digit |
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Java is case sensitive - Total, total, and TOTAL
are different identifiers |
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By convention, Java programmers use different
case styles for different types of identifiers, such as |
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title case for class names - Lincoln |
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upper case for constants - MAXIMUM |
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Sometimes we choose identifiers ourselves when
writing a program (such as Lincoln) |
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Sometimes we are using another programmer's
code, so we use the identifiers that they chose (such as println) |
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Often we use special identifiers called reserved
words that already have a predefined meaning in the language |
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A reserved word cannot be used in any other way |
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Spaces, blank lines, and tabs are called white
space |
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White space is used to separate words and
symbols in a program |
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Extra white space is ignored |
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A valid Java program can be formatted in many
ways |
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Programs should be formatted to enhance
readability, using consistent indentation |
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See Lincoln2.java (page 37) |
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See Lincoln3.java (page 38) |
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There are four programming language levels: |
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machine language |
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assembly language |
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high-level language |
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fourth-generation language |
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Each type of CPU has its own specific machine
language |
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The other levels were created to make it easier
for a human being to read and write programs |
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A program must be translated into machine
language before it can be executed on a particular type of CPU |
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This can be accomplished in several ways |
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A compiler is a software tool which translates source
code into a specific target language |
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Often, that target language is the machine
language for a particular CPU type |
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The Java approach is somewhat different |
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The Java compiler translates Java source code
into a special representation called bytecode |
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Java bytecode is not the machine language for
any traditional CPU |
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Another software tool, called an interpreter,
translates bytecode into machine language and executes it |
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Therefore the Java compiler is not tied to any
particular machine |
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Java is considered to be architecture-neutral |
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There are many environments for developing Java
software: |
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Sun Java Development Kit (JDK) |
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Sun Forte for Java |
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Borland JBuilder |
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MetroWerks CodeWarrior |
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Microsoft Visual J++ |
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Symantec Café |
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Monash BlueJ |
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Though the details of these environments differ,
the basic compilation and execution process is essentially the same |
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The syntax rules of a language define how we can
put together symbols, reserved words, and identifiers to make a valid
program |
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The semantics of a program statement define what
that statement means (its purpose or role in a program) |
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A program that is syntactically correct is not
necessarily logically (semantically) correct |
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A program will always do what we tell it to do,
not what we meant to tell it to do |
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A program can have three types of errors |
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The compiler will find syntax errors and other
basic problems (compile-time errors) |
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If compile-time errors exist, an executable
version of the program is not created |
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A problem can occur during program execution,
such as trying to divide by zero, which causes a program to terminate
abnormally (run-time errors) |
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A program may run, but produce incorrect
results, perhaps using an incorrect formula (logical errors) |
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The last one or two sections of each chapter of
the textbook focus on graphical issues |
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Most computer programs have graphical components |
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A picture or drawing must be digitized for
storage on a computer |
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A picture consists of pixels, and each pixel is
stored separately |
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A black and white picture can be stored using
one bit per pixel (0 = white and 1 = black) |
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A colored picture requires more information;
there are several techniques for representing colors |
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For example, every color can be represented as a
mixture of the three additive primary colors Red, Green, and Blue |
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In Java, each color is represented by three
numbers between 0 and 255 that collectively are called an RGB value |
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Each pixel can be identified using a
two-dimensional coordinate system |
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When referring to a pixel in a Java program, we
use a coordinate system with the origin in the top-left corner |
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Chapter 1 has focused on: |
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components of a computer |
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how those components interact |
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how computers store and manipulate information |
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computer networks |
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the Internet and the World Wide Web |
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programming and programming languages |
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graphic systems |
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Notes
