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Annotated log
Java - Basic Tools example from a Well House Consultants training course
More on Java - Basic Tools [link]

This example is described in the following article(s):
   • Using java, javac, jar, and CLASSPATH - a simple example - [link]

Source code: javalog.001 Module: A502
# Annotated log of command line Java compiles and runs

-----> Which Java runtime engine is the default?

wizard:~ graham$ java -version
java version "1.6.0_20"
Java(TM) SE Runtime Environment (build 1.6.0_20-b02-279-10M3065)
Java HotSpot(TM) 64-Bit Server VM (build 16.3-b01-279, mixed mode)
wizard:~ graham$

-----> Which Java compilr is the default?

wizard:~ graham$ javac -version
javac 1.6.0_20
wizard:~ graham$

-----> Edit source file (type in a new java program)
        Compile it via javac
        Run it via java
        (note - .java on the compile, but no extension as you run

wizard:java graham$ vi Annie.java
wizard:java graham$ javac Annie.java
wizard:java graham$ java Annie
Java refresh!
wizard:java graham$

-----> What files do we now have?
        Source in Annie.java
        Class file (compiled code which we ran from) in Annie.class

wizard:java graham$ ls
Annie.class Annie.java
wizard:java graham$

-----> What if we want to edit one source file to make another class source?
        Really we should use inheritance, but if we insist we need to edit source
        as the file must have the same name as the class

wizard:java graham$ cp Annie.java Bella.java
wizard:java graham$ javac Bella.java
Bella.java:2: class Annie is public, should be declared in a file named Annie.java
public class Annie {
       ^
1 error
wizard:java graham$ vi Bella.java

------> What if you call another method?
        It must exist at compile time!

wizard:java graham$ javac Bella.java
Bella.java:5: cannot find symbol
symbol : method walk()
location: class Bella
                walk();
                ^
Bella.java:7: cannot find symbol
symbol : method walk()
location: class Bella
                walk();
                ^
2 errors
wizard:java graham$ vi Bella.java

-----> A proper compile and run!

wizard:java graham$ javac Bella.java
wizard:java graham$ java Bella
Who's knicked me shoes? I'll have to drive
Java refresh!
Who's knicked me shoes? I'll have to drive
wizard:java graham$

------> Create another class which calls an external reference
        That reference must be available for checking at compile time

wizard:java graham$ cp Bella.java Chloe.java
wizard:java graham$ vi !$
vi Chloe.java
wizard:java graham$ javac Chloe.java
Chloe.java:6: cannot find symbol
symbol : variable Debbie
location: class Chloe
                Debbie.run();
                ^
Chloe.java:8: cannot find symbol
symbol : variable Debbie
location: class Chloe
                Debbie.run();
                ^
2 errors
wizard:java graham$ vi Chloe.java
wizard:java graham$ vi Debbie.java

------> Notice how I compile Chloe.java ... and internally it decides
        that it must compile Debbie too.

        Java is case sensitive ... protected and not Protected !!

wizard:java graham$ javac Chloe.java
./Debbie.java:2: class, interface, or enum expected
Protected class Debbie {
^
1 error
wizard:java graham$

------> Correct Debbie, recompile Chloe, and it works!

wizard:java graham$ vi Debbie.java
wizard:java graham$ javac Chloe.java
wizard:java graham$ java Chloe
Who's knicked me shoes? I'll have to drive
Puffered!
Java refresh!
Puffered!
Who's knicked me shoes? I'll have to drive
wizard:java graham$

--------> SECTION ON .jar FILES

------> Put all the class files into a jar

wizard:java graham$ ls
Annie.class Bella.class Chloe.class Debbie.class
Annie.java Bella.java Chloe.java Debbie.java
wizard:java graham$ jar cf jam.jar *.class

--------- and CAREFULLY remove all the .class files

wizard:java graham$ ls -l
total 72
-rw-r--r-- 1 graham staff 417 7 Jul 10:30 Annie.class
-rw-r--r-- 1 graham staff 240 7 Jul 10:31 Annie.java
-rw-r--r-- 1 graham staff 547 7 Jul 10:35 Bella.class
-rw-r--r-- 1 graham staff 411 7 Jul 10:35 Bella.java
-rw-r--r-- 1 graham staff 589 7 Jul 10:39 Chloe.class
-rw-r--r-- 1 graham staff 650 7 Jul 10:43 Chloe.java
-rw-r--r-- 1 graham staff 389 7 Jul 10:39 Debbie.class
-rw-r--r-- 1 graham staff 96 7 Jul 10:39 Debbie.java
-rw-r--r-- 1 graham staff 2122 7 Jul 10:47 jam.jar
wizard:java graham$ rm *.class
wizard:java graham$ ls
Annie.java Bella.java Chloe.java Debbie.java jam.jar

------> Try to run one of the classes and it won't work

wizard:java graham$ java Chloe
Exception in thread "main" java.lang.NoClassDefFoundError: Chloe
Caused by: java.lang.ClassNotFoundException: Chloe
        at java.net.URLClassLoader$1.run(URLClassLoader.java:202)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:307)
        at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:248)

-----> Set the CLASSPATH to point to the jar and you can now
        run straight from the jar.

wizard:java graham$ export CLASSPATH=jam.jar
wizard:java graham$ ls
Annie.java Bella.java Chloe.java Debbie.java jam.jar
wizard:java graham$ java Chloe
Who's knicked me shoes? I'll have to drive
Puffered!
Java refresh!
Puffered!
Who's knicked me shoes? I'll have to drive
wizard:java graham$

------> Alter the original source, recomiple and run ....
        and you'll find the old code still running because your
        class path only points at the .jar

wizard:java graham$ vi Bella.java
wizard:java graham$ javac !$
javac Bella.java
wizard:java graham$ java Bella
Who's knicked me shoes? I'll have to drive
Java refresh!
Who's knicked me shoes? I'll have to drive
wizard:java graham$ ls
Annie.java Bella.class Bella.java Chloe.java Debbie.java jam.jar

------> Modify the CLASSPATH so it looks in the current directory
        ahead of anythin else in the old path.

wizard:java graham$ export CLASSPATH=.:$CLASSPATH
wizard:java graham$ java Bella
Who's removed me shoes? I'll have to drive
Java refresh!
Who's removed me shoes? I'll have to drive

------> Check that the stuff from the jar also works!

wizard:java graham$ java Annie
Java refresh!
wizard:java graham$ ls
Annie.java Bella.class Bella.java Chloe.java Debbie.java jam.jar

------> Look and see what's in the jar!

wizard:java graham$ jar tf jam.jar
META-INF/
META-INF/MANIFEST.MF
Annie.class
Bella.class
Chloe.class
Debbie.class
wizard:java graham$ jar tvf jam.jar
     0 Wed Jul 07 10:47:04 BST 2010 META-INF/
    60 Wed Jul 07 10:47:06 BST 2010 META-INF/MANIFEST.MF
   417 Wed Jul 07 10:30:46 BST 2010 Annie.class
   547 Wed Jul 07 10:35:00 BST 2010 Bella.class
   589 Wed Jul 07 10:39:54 BST 2010 Chloe.class
   389 Wed Jul 07 10:39:54 BST 2010 Debbie.class

-------> Run the class that's in the current directory.
        Delete it, run again, and you'll find that it
        runs the class that's in the jar which was
        being masked previously.

wizard:java graham$ java Bella
Who's removed me shoes? I'll have to drive
Java refresh!
Who's removed me shoes? I'll have to drive
wizard:java graham$ rm Bella.class
wizard:java graham$ java Bella
Who's knicked me shoes? I'll have to drive
Java refresh!
Who's knicked me shoes? I'll have to drive
wizard:java graham$

Learn about this subject
This module and example are covered on the following public courses:
 * Deploying Apache and Tomcat
 * Deploying Java Applications on Linux / Unix
Also available on on site courses for larger groups

Books covering this topic
Yes. We have over 700 books in our library. Books covering Lamp deployment are listed here and when you've selected a relevant book we'll link you on to Amazon to order.

Other Examples
This example comes from our "Java - Basic Tools" training module. You'll find a description of the topic and some other closely related examples on the "Java - Basic Tools" module index page.

Full description of the source code
You can learn more about this example on the training courses listed on this page, on which you'll be given a full set of training notes.

Many other training modules are available for download (for limited use) from our download centre under an Open Training Notes License.

Other resources
• Our Solutions centre provides a number of longer technical articles.
• Our Opentalk forum archive provides a question and answer centre.
The Horse's mouth provides a daily tip or thought.
• Further resources are available via the resources centre.
• All of these resources can be searched through through our search engine
• And there's a global index here.

Web site author
This web site is written and maintained by Well House Consultants.

Purpose of this website
This is a sample program, class demonstration or answer from a training course. It's main purpose is to provide an after-course service to customers who have attended our public private or on site courses, but the examples are made generally available under conditions described below.

Conditions of use
Past attendees on our training courses are welcome to use individual examples in the course of their programming, but must check the examples they use to ensure that they are suitable for their job. Remember that some of our examples show you how not to do things - check in your notes. Well House Consultants take no responsibility for the suitability of these example programs to customer's needs.

This program is copyright Well House Consultants Ltd. You are forbidden from using it for running your own training courses without our prior written permission. See our page on courseware provision for more details.

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