Hi everyone, I have been programming in java for a while but I haven't used external .jar archives previously. Now, I am faced with the current situation: 1- I have a java file (SNPHarvester.java) located in my /home directory. 2- Under: /home/lib/ I have two .jar archives, namely: commons-math-1.2.jar and weka.jar 3- In the sourcecode (SNPHarvester.java), I have the following import statements: import weka.core.Utils; import org.apache.commons.math.distribution.ChiSquaredDistribution; import org.apache.commons.math.distribution.ChiSquaredDistributionImpl; Now: my weka.jar has the structure: weka/core/Utils.class my commons-math-1.2.jar contains the structure: /org/apache/commons/math/distribution/ChiSquaredDistribution.class and ChiSquaredDistributionImpl.class - However, notice the name of the .jar archive - unlike my weka.jar, commons-math-1.2 does not show up in the import statement. Now, when I compile using the following: javac -cp ".:lib/weka.jar:lib/commons-math-1.2.jar" SNPHarvester.java it outputs the following: [zibrahimbrc@bignode lib]$ javac -cp ".:lib/weka.jar:lib/commons-math-1.2.jar" SNPHarvester.java javac: file not found: SNPHarvester.java Usage: javac <options> <source files> use -help for a list of possible options Which I am assuming it's okay. However, the following exception is generated when I run the corresponding .class file: [zibrahimbrc@bignode snp_harvester]$ java SNPHarvester Exception in thread "main" java.lang.NoClassDefFoundError: org/apache/commons/math/distribution/ChiSquaredDistribution Caused by: java.lang.ClassNotFoundException: org.apache.commons.math.distribution.ChiSquaredDistribution 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) Could not find the main class: SNPHarvester. Program will exit. It's not finding the classes in commons-math-1.2.jar Any ideas about what I'm doing wrong? your help is highly appreciated. Thank you very much in advance.