Download AS/400 Java

Java
▮ How the class works
▮ Java programming concepts
▮ Downloading the JDK
▮ Java coding and executing example
Chapter 1
© copyright Janson Industries 2014
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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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Copyright 2014 by Janson Industries
You can skip the video and go
straight to the instructions
Once done with
instruction, close window
and try exercises
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Copyright 2014 by Janson Industries
The first puzzle will start
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Copyright 2014 by Janson Industries
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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Copyright 2014 by Janson Industries
Click Continue to go
to next puzzle
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Copyright 2014 by Janson Industries
Click Continue to go
to next puzzle
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Copyright 2014 by Janson Industries
If you can't figure it out, scroll
down and click the help links
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Copyright 2014 by Janson Industries
How Class Works
▀
▀
There's an entire COP1000 set
of lessons at
http://learn.code.org/
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Copyright 2014 by Janson Industries
Unplugged activites have the
theory – good to read first
Then tackle the puzzles
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Copyright 2014 by Janson Industries
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
© copyright Janson Industries 2014
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
© copyright Janson Industries 2014
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?
Chapter 1
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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