Exception in thread "main" java.lang.NoClassDefFoundError: javax/comm/SerialPortEventListener

http://java.sun.com/products/javacomm

The error message is from your java runtime.  Your code is trying to use the javax.comm.SerialPortEventListener, but the java runtime can't find that class.  

Since your code is obviously using that class and compiling, this must mean that your compiler and your runtime don't have access to the same set of classes.  Do you compile with an additional -classpath?  Is your java runtime the same version as your java compiler?  Is there a default java runtime installed somewhere on your OS that is taking over when you try to run your program?

Hi,

I ran this program after installing java com package. I am using the same version for both runtime and compiler, that is, java 1.4.2_04. I initially had 2 runtime installed on my system but then i removed everything and reinstalled java 1.4.2_04 couple of weeks back. If there is another version taking control, then how do I find that? I dont compile with additional -classpath. I have set the classpath variable PATH = c:\j2sdk1.4.2_04\bin;

Thanks,
Seema

see the install instructions for javacomm and ensure you have done everything instructed

Try the -v option with java and javac to see if they are the same versions. (or is it -V;  I forget).

I am still not able to figure out the problem.. I checked at all places and removed all the java components on the computer but Java Runtime and SDK. I followed the same steps to install java.comm package as given in the installation procedure in it. What else can be the problem? Thanks Seema

where have you put the javacomm jar?

This is the link to the java comm.jar file :
      C:\j2sdk1.4.2_04\jre\lib\ext
This is the link to javax.comm.properties :
      C:\j2sdk1.4.2_04\jre\lib
This is the link to win32com.dll :
      C:\j2sdk1.4.2_04\jre\bin

Thanks,
Seema

I followed whatever was given in the instructions in the Java comm package. I installed everything in JRE folder asI already mentioned in the link above. I looked in the program files but I couldn't see JRE folder where I could install all these files :(

Again,
C:\j2sdk1.4.2_04\jre\lib\ext\comm.jar
C:\j2sdk1.4.2_04\jre\lib\javax.comm.properties
C:\j2sdk1.4.2_04\jre\bin\win32com.dll

Thanks,
Seema

Thats the JDK installation (which includes a VM), the default JDK installation will install an additional JRE which is the one used when you run a class by default.

another thing to try would be to use the jdk's vm explicitly:


C:\j2sdk1.4.2_04\bin\java MyClass

I didnt get that error after putting all my files in C:\j2sdk1.4.2_04\bin\ directory. But now its only looking at the COM port and not doing anything. This is a fully ruuning program and is tested on other computer but doesnt work on this system.  Is it fine if I provide more details through email at ee@objects.com.au?

Thanks,
Seema

yopu shouldn't have had to move any files. what did u move exactly?

Then may be I didnt get by what you wrote:
  "another thing to try would be to use the jdk's vm explicitly:
        C:\j2sdk1.4.2_04\bin\java MyClass "

I moved all the java files that I was compiling with javac. My files are GPSReceiver.java, Location.java , RockData.java, RockHeader.java, RockMessage.java, RockMessage1000.java, and Tools.java. Thanks Seema