Transcript AS/400 Java

Java
▮ How the class works
▮ Java programming concepts
▮ Downloading the JDK
▮ Java coding and executing example
Chapter 1
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PP Presentations
▮ Can be viewed online or downloaded
▮ Go to:
▮ web.fscj.edu/Janson/COP2551
▮ For all presentations and class files
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Or you can go to my school website
(web.fscj.edu/Janson) and click on this link
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This presentation is 4thed.Ch01.ppt
Click file name (link) to view online…
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Or choose Save as
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How Class Works
▮ Do the non-graded exercises first
▮ They will help you solve the graded assgs
▮ I can help you with these assgs/probs
▮ Keep track of the probs and solutions
▮ You will make the same mistakes many
times
▮ Graded assgs (the Tutorials in the
chapter and Challenge Exs) are for you
(and you alone) to complete
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How Class Works
▮ Tutorials (chapters 1-7) are 10% of your
grade
▮ Challenge Exercises (Review Exercises at
the end of chapters 1-7) are 20%
▮ Extra Credit (chapters 8-10 Tutorials) are
extra 5%
▮ Must do non-graded assgs to get
credit for graded assgs
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How Class Works
▮ Tests are composed of 50 multiple
choice questions
▮ To get an A you will have to do the
Review Exercises
▮ Strongly advise you to do all of them
▮ You can also do the end of chapter
challenge exercises
▮ If you can do all these you probably know
the material
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How Class Works
▮ If you come to a lecture, listen and take
notes
▮ You will not learn the material by listening
to the lecture and viewing the slides once
▮ You need to study/do the material covered
in the lecture and examples
▮ And doing an exercise correctly once doesn’t
necessarily mean you know it!
▮ This class assumes you all have WIN 7
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How Class Works
▮ You will need a thumb drive for the class
to store all your assgs
▮ Suggestion: create a file named ICE or
IFFOUND and put in some contact info
for yourself
▮ This may mean you will get it back when
you lose it ;-)
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Classroom Computers
▮ The anti-virus s/w does not play nicely
with RAD
▮ You need to sign on to the computers
using the following:
▮ User id
.\ibm
▮ PW
cop2551
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How Class Works
▀
▀
▀
How long has it been since you
took COP1000?
Code.org
Uses videos and games to get
across the basic programming
structures which you are already
expected to understand
♦
http://learn.code.org/hoc/1
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You can skip the video and go
straight to the instructions
Once done with
instruction, close window
and try exercises
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The first puzzle will start
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When puzzle finished will
allow you to continue to the
next one or you can click to
skip ahead
There may be more
instructions, click
X's to close
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Click Continue to go
to next puzzle
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Click Continue to go
to next puzzle
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If you can't figure it out, scroll
down and click the help links
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How Class Works
▀
▀
There's an entire COP1000 set
of lessons at
http://learn.code.org/
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Unplugged activites have the
theory – good to read first
Then tackle the puzzles
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Java Concepts
▮ Java source code stored in files with an
extension of .java
▮ The source code is “compiled”, meaning:
▮ Translated into bytecode
▮ Bytecode stored in class files (files with an
extension of .class)
▮ Bytecode is a “cross-platform program
representation” that is non-executable
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Java Concepts
Cust.java
(Java file)
Cust.class
(Class file)
Java source
code
Editor
Compiler
Java source
code
Programmer
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Java
bytecode
javac Cust.java
Programmer
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Java Concepts
▮ Review: files with an extension of .java
contain source code
▮ Review: files with an extension of .class
contain “bytecode”
▮ .java files are “compiled” (javac) to create
.class files
▮ Bytecode is a cross-platform program
representation that is non-executable
▮ New: bytecode needs to be translated to
machine language (java)
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Java Virtual Machine (JVM)
▮ JVM is “the place” (i.e. s/w) where the
.class files (i.e. programs) are translated
▮ The JVM is invoked with the java
command
▮ The JVM translates bytecode into
machine language and sends to CPU for
execution (i.e. program is run)
▮ Therefore, each "type" of computer
needs a unique JVM
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Java Concepts
Cust.java
(Java file)
Cust.class
(Class file)
Java source
code
Editor
Java source
code
Programmer
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CPU
Java
bytecode
Compiler
javac Cust.java
Programmer
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JVM
main method
in Machine
Language
java Cust
Programmer
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Java Virtual Machine (JVM)
▮ To run a java application on a computer
you must download a JVM/JRE (java
runtime environment)
▮ Oracle (and many other vendors) offer
▮ Oracle has a JDK (Java Development Kit)
that includes a JRE (and compiler)
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JDK (aka JSDK)
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JDK on the PC
▮ Java JDK 8 is an example
▮ Use IE (not Chrome) to download the JDK:
▮ http://www.oracle.com/technetwork/java/javase
/downloads/index.html
▮ Select the latest version
▮ Click on the JDK download button for the latest
update (i.e. JDK 8, or JDK8u20, etc.)
▮ Select the JDK for your computer (i.e. Windows)
▮ Download to thumb drive (G:) or your C drive
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JDK on the PC
▮ To install the JDK:
▮ Run jdk-8(u#)-windows-i586-p.exe (where # is
the latest version and update numbers)
▮ During the install, create folders to hold the JDK
and JRE called jdk and jre
▮ Delete the original .exe file jdk-8(u#)-windows-
i586-p.exe
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Select the latest JDK version
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Scroll down and click the accept agreement radio button
Double click the operating system of the lab computers
(Windows x86)
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Specify to save the file by clicking the Save drop down
button and then Save As
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Create a folder called jdkzip on your thumb drive (or the
C: if you will always being work on that same computer)
and save the .exe file to jdkzip
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Using My Computer open the jdkzip folder
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JDK on the PC
▮ Only takes
up 165 meg
▮ Final install
will take up
~180 meg
▮ Run the exe file by
double clicking
▮ Click the Next button
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If you get this, you downloaded the wrong JDK
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Or this (or any other msg), you downloaded the wrong
JDK
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Accept the default components
(notice the JRE is just one part of the JDK)
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You can control where the JDK is installed
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by clicking the Change... button
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To save on typing later, we’ll change directory to just JDK i.e. E:\JDK
(or C:\JDK\) then click the OK button
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JDK install window redisplayed with new location
Click Next
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Shows where JRE will be installed. Change to…
Some students tell me this screen doesn’t appear, if it
doesn’t – no problem, skip the next two slides.
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Choose drive to save to, then click Make New Folder
Then specify jre, click OK
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JRE install window redisplayed with new location, click
Next
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You may have to shut down some running apps
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And again…
Depending on where you installing, could take a while (a thumb drive
will take longer than a hard drive
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Two folders called jdk and jre are created (verify with
My Computer)
Delete jdkzip\jdk-8(u#)-windows-i586-p.exe and
click the Close button
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To verify that you installed correctly, display the
contents of jdk/bin folder and make sure you have two
executable files called javac and java
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Running a pgm
▮ When you run a application in Windows,
you are specifying an executable file
name
▮ Executable files contain machine
language
▮ On Windows machines these files have
names that end in .exe
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▮ For instance, clicking
the IE icon tells
Windows to “run”
iexplore.exe in
C:\Program
Files\Internet Explorer\
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▮ C:\Program Files\Internet Explorer\iexplore.exe is a
fully qualified file name
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Running a pgm
▮ If a fully qualified file name is not
specified, Windows searches
▮ 1. The default (aka current) directory
▮ 2. The locations stored in the the
Environment Variable called PATH
▮ I.e. path holds all the locations Windows
should search when an unqualified file name
is specified
▮ You can control the value of the Path variable
▮ Let’s prove it!!
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Running a pgm
▮ In command prompt we specify iexplore.exe
▮ You get the “Not recognized” message
▮ Now specify fully qualified file name (in quotes)
▮ Internet Explorer is started
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Running a pgm
▮ Now we will set the path value
▮ path = "C:\Program Files\Internet Explorer\"
▮ In command prompt we specify iexplore.exe
▮ Internet Explorer started
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Running a pgm
▮ JDK/bin must be in the PC’s path for
Windows to access the compile (javac) and
run (java) commands
▮ Path holds the locations to search for files
▮ Several ways to define path locations
▮ Each time you go to the command prompt
(depending on where jdk installed) enter
▮ path=f:\jdk\bin
or
▮ path=c:\jdk\bin
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Running a pgm
Start Notepad, enter source code, and save file with type of java
F:\Customer.java (must specify type as All Files)
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Running a pgm
To run, bring up the Command Prompt by clicking:
Start, Accessories, Command Prompt
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Running
▮ When javac and java commands are run, at
first they do the same thing as Windows
▮ They check the default directory for the java and
bytecode files
▮ If files not there, "file not found" msg displayed
▮ 2 solutions
▮ Change current directory to the location of the files
with the CD (change directory) command
▮ CD F:\, hit Enter, then type F:, hit Enter again
▮ Include files location in classpath variable
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Running
▮ 1. Issue the path command so that jdk/bin is in
the path
▮ 2. If necessary, change the default path to the
location of the java file (i.e. F:\ )
(type CD F:\, hit Enter, then type F:, hit Enter)
▮ 3. Convert to bytecode (javac Customer.java)
▮ 4. Convert bytecode to machine language and
run the program (java Customer)
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Running
Prompt shows the default directory
Customer.java is on F:\
current directory is H:\
so “file not found”
Must change current directory to
location of Customer.java (i.e. F:\)
Customer.java found cause
default directory is F:
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Running a pgm
▮ It’s that easy!
▮ But not very pretty both in terms of
▮ The application function and appearance
▮ The development environment
▮ So we’ll change how we do several things
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Making Programming Easier
▮ Easier ways to set up path and default dir
▮ Use an IDE (Integrated Development
Environment) instead of notepad
▮ Eclipse
▮ Rational Application Developer (RAD)
▮ NetBeans
▮ Learn more java so that the application
GUI is PURTY
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JDK Install Problems?
▮ Error 1723 occurred in the installer
package
▮ Lot’s of possible reasons
▮ Click here for some suggestions
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Possible Problems?
▮ javac or java command is not recognized
▮ Why?
Path not defined correctly. Common mistakes: wrong
drive letter, incorrect directory name(s), extra spaces after
bin, when installing you mixed up jdk and jre directories
▮ Customer file not found:
NoClassDefFoundError,
ClassNotFoundException, could not find the main class
▮ Why?
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Current directory not where Customer file is located (or
per book, Classpath not defined correctly) or file name not
specified correctly (extra spaces, etc.)
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Possible Problems?
▮ When there are Java syntax errors, JVM will
show:
▮ A message with useful info
▮ File name: Customer.java
▮ Line number that has the error: 10
▮ What the problem is: ‘;’ expected
▮ The source code statement(s) that have errors
with ^ under where it thinks there are problems
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Possible Problems?
▮ Common Java syntax errors
▮ Upper case/lower case letters are
different
▮ If example shows upper case letter, you must
use upper case letter
▮ Forward slash/ back slash\ are different
▮ println (means: print line) not printIn
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Changes
▮ We’re going to use RAD instead of
notepad
▮ Ch01a slides are next
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But first….
▮ Class exercise:
▮ Download the JDK to the F: or C: or...
▮ I suggest your thumb drive
▮ Install it
▮ Setup the path and default directory
▮ Enter the source code (exactly as shown on
the slide)
▮ javac and java to run the program
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