Thread: cannot find symbol (in a jar file)

It has been a while since I have programmed using java. I'm
in the process relearning java and I have run into a problem.
I am trying to create a java program that calls a method in
a package method stored in a library jar file.

BTW, my version of java is:
java version "1.8.0_301"
Java(TM) SE Runtime Environment (build 1.8.0_301-b09)
Java HotSpot(TM) 64-Bit Server VM (build 25.301-b09, mixed mode)

My sample jar file is "Pack.jar", using a source file named, "Pack.java",
and shown below.

I have also created a java file named, "Call.java" whose purpose
is to access the the methods within the Pack.jar file. This file is
shown below also.

The directory structure is:


...
|
bfs
____________________________
| |
javaPackage lib
|
_____________________________
| |
| |
jarPackage jarCaller
| |
george Call.java
|
washington
|
Pack.java

The Pack.java file has a main() method that allows me to test if
the Pack class is working as I expect. I have a test c-shell script
named, "run". When I run a test on Pack.class, it yields the
following output:


% run
1: Start Pack class.
2: Created Pack instance.
3: Running message() method of Pack class.
4: End Pack class.

No problem here, the script successfully pushes to the directory
containing, "bfs", and runs java using the full path from that
directory to the directory where the Pack class resides. I run
the following command to get the out when the "run" script is
executed.

java bfs/javaPackage/jarPackage/george/washington/Pack

The Pack main() method successfully calls the message() method of the
Pack class.

A Pack.jar file is then created with:

jar -cf Pack.jar Pack.class

The jar file is copied to a local library directory with:

cp Pack.jar .../bfs/lib/Pack.jar

Next I go to the jarCaller directory and compile the Call.java class.
I compile with the following:

javac -classpath .:../bfs/lib/Pack.jar ./Call.java

In the first pass of Call.java, the main() method simply creates an
instance of the Pack class using the Pack class constructor. When run,
it successfully creates an instance of the Pack class and the Call
class prints the message:

Pack instance created

In the second pass, I add the following line to the Call main() method:

pack.message();

When I try to compile the Call.class, it now gives the error message:

./Call.java:29: error: cannot find symbol
pack.message();

NOTE: 'pack' is the variable created with:
Pack pack = new Pack();

I am baffled by this error message.


The possible causes for the error message that I can think of are:
1) The Pack class does not have a message() method.
- This is not the case, since I run a test in the Pack class
that runs the message() method.
2) The java compiler is not finding the Pack.jar class.
- This is not the case. I know the Pack.jar class is found
because if I comment out the pack.message() line, the
Call class succesfully calls the Pack class constructor
and I can then run the Call main() method.
3) The message() method is not public.
- The Pack class message method is public.


// *************************************************
// Source codce: Pack.java
// ************************

package bfs.javaPackage.jarPackage.george.washington;

public class Pack {

private Pack() {
System.out.println("\t2: Created Pack instance.");
}

public String message() {
return("Running message() method of Pack class.");
}

public static void main(String args[]) {
System.out.println("\t1: Start Pack class.");
Pack pack = new Pack();
System.out.println("\t3: " + pack.message());
System.out.println("\t4: End Pack class.");
}
}


// *************************************************
// Source code: Call.java
// ************************

import bfs.javaPackage.jarPackage.george.washington.Pack;

public class Call {
public static void main(String args[]) {
System.out.println("This is the Call class.");
Pack pack = new Pack();
if ( pack == null ) {
System.err.println("pack is null.");
System.exit(-1);
}
else {
System.out.println("Pack instance created.");
}
pack.message(); // when this line is commented out. The file
// can be compiled and run w/o error.
}
}

Norm,

First, thank you very much for your help on this issue!

I think I understood what you suggested. I changed the creation
of my jar file so that it is now created in the parent directory
of the 'bfs' directory.

Now when I run:

jja@sutton: unzip Pack.jar

The results show:

Archive: Pack.jar
creating: META-INF/
inflating: META-INF/MANIFEST.MF
inflating: bfs/javaPackage/jarPackage/george/washington/Pack.class

whereas, previously the results were:

Archive: Pack.jar
creating: META-INF/
inflating: META-INF/MANIFEST.MF
inflating: Pack.class

If I place, Pack.jar in the same directory as the Call.java class and
run:

javac -cp .ack.jar Call.java

I am still getting an error:

Call.java:15: error: cannot find symbol
pack.message();
^
symbol: method message()
location: variable pack of type Pack


I am still missing someting from your instructions or I misunderstood
your feedback. :-(

Jim

I have double checked the Pack class and it does the message method is declared public:

>>> public String message() {
>>> return("Running message() method of Pack class.");
>>> }

The Pack class constructor should be public and I have fixed that. Thank you.

I'm going to put this thread on hold. While it is on hold, I am going to do some experimenting with some simpler cases and see if I can work my way back to this case. My experimenting could be a few days, maybe even a week, but I shall return to this case.

This can be closed. As I mentioned earlier, I did some experimenting, starting with a simple case with no hierarchy, then added the hierarchy that I need and got it working.

To Norm, my thanks for the help.