Error in launching Java application on Eclipse

Question

I just installed Eclipse (2020 version) and IBM ILOG CPLEX (12.6.9 version), on Windows 10, to run a Java code that I already have.

The code uses Java API of CPLEX, so I followed these few instructions (on CPLEX Official Page) - they explains to set a jar and a dll filepaths - to set up Eclipse for using Java API of CPLEX.

I followed those steps, but when I launch the execution I get this error:

Error: Unable to initialize main class Scheduler_1 Caused by: java.lang.NoClassDefFoundError: ilog/concert/IloNumExpr

Additional information: After navigating to Run > Run Configurations... > Java Application , and selecting Arguments tab , if I click on Show Command Line , a dialog, which shows this output lines, appears (I don't know if it's correct):

`C:\Users\MY_USERNAME\Downloads\eclipse-java-2020-12-R-win32-x86_64\eclipse\plugins\org.eclipse.justj.openjdk.hotspot.jre.full.win32.x86_64_15.0.1.v20201027-0507\jre\bin\javaw.exe`

`-Djava.library.path=CPLEX_Studio_Community129/cplex/bin/x64_win64`

`-Dfile.encoding=Cp1252`

`-p "C:\Program Files\IBM\ILOG\CPLEX_Studio_Community129\cplex\lib\cplex.jar"`

`-classpath "C:\Users\MY_USERNAME\eclipse-workspace\proj1\bin"`

`-XX:+ShowCodeDetailsInExceptionMessages Scheduler_1`

Is there anyone who know which could be the cause of the error which I encounter?

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To add more details: these are the steps I followed:

1. Download of Eclipse 2020-12 ".zip" file and saved in "Download" folder, and download of CPLEX 12.6.9 "exe" file

2. Extract Eclipse 2020-12 "zip" into a folder (with the same name of the "zip") inside "Download", then I install both Eclipse and CPLEX (on Windows 10), by double-clicking on their respective "exe" files

3. Open Eclipse, and created a new Eclipse Java Project, called proj1

4. Added four ".java" source files (copy-pasted from another folder of my PC) inside proj1/src/

5. On Eclipse GUI:

   • Project > Properties > Java Build Path > Libraries
   • When the dialog appears, click the button Add External JARs
   • Then after browsing the location, I select the file named cplex.jar .

6. On Eclipse GUI:

   • Run > Run Configurations... > Java Application
   • When the dialog appears, I go to the Main tab , and select my Main Class (called Scheduler_1 )
   • Then, I go to the Arguments tab , I select VM arguments , and add the path to the CPLEX library, so in my case: -Djava.library.path=CPLEX_Studio_Community129/cplex/bin/x64_win64 , which is the path to cplex1290.dll

7. I run the Java application, and I get the error:

Error: Unable to initialize main class Scheduler_1 Caused by: java.lang.NoClassDefFoundError: ilog/concert/IloNumExpr

Besides, IloNumExpr is not even used in my code, and, anyway, it is contained in cplex.jar (I checked by myself).

Other details: this is the directory structure of my project (which I could see from Package Explorer , which is part of the Eclipse Workspace ):

• proj1
  • src
    • (default packages) : it contains four ".java" files (which I copy-pasted from another folder of my PC)
  • JRE System Library
  • Referenced Library : it contains cplex.jar (external library added by me)

Answer 1

Finally it seems I solved my issue. I post here what works for me for anyone who will encounter the same error.

I navigated to Project -> Properties -> Build Path , then I clicked on Dependencies Tab and I removed cplex.jar from Modulepath Entries and I added it to Classpath Entries .

Now, the previous error is solved.