This is the problem:

import org.apache.commons.math3;

That's trying to import a package - you can't do that. You have to either use a wildcard import:

import org.apache.commons.math3.*;

or import a specific type:

import org.apache.commons.math3.SomeTypeHere;

In your case it sounds like you actually want:

import org.apache.commons.math3.distribution.EnumeratedIntegerDistribution;

I've tried a sample class with just that import and the jar file downloaded from Apache, and it works fine.

Did you unpack that Apache JAR and add the .class files to your application? Why didn't you just add the JAR to your CLASSPATH?

You should not be depending on a CLASSPATH environment variable. Better to use the -classpath option for javac.exe when you compile and java.exe when you run.

I cannot reproduce. After adding JAR file to dependencies and adding an import statement on top of the class file everything worked as expected. Maybe try to change scope?

Dependencies:

Class file:

Try running the following commands and examine the output:

$ mvn dependency:tree
$ mvn help:effective-pom

Look for commons-lang, maybe something will draw your attention like excludes or dependency overrides. Also, is:

$ mvn dependency:copy-dependencies

copying commons-lang JAR to your target?

I was having same issue then realized that the version of commons-io getting picked up was lower than what I need (2.4)....I need to Override the already managed version as below to get the right one picked up:

<dependency>
     <groupId>commons-io</groupId>
     <artifactId>commons-io</artifactId>
     <version>2.4</version>
 </dependency>

it started working now. I downloaded commons-io-2.4 from a different resource and imported to my project. Thanks

With few minute changes I am able to execute this code:-

    CommandLineParser parser = new PosixParser();
    Options options = new Options();
    options.addOption("a", true, "First parameter"); 
    args=new String[]{"-a abc"};

    try {
        CommandLine commandLine = parser.parse(options, args );    
        System.out.println(commandLine.getOptionValue("a"));
    } catch (ParseException e1) {
        e1.printStackTrace();
    }


Output :-  abc

In my pom.xml :-

  <dependency>
    <groupId>commons-cli</groupId>
    <artifactId>commons-cli</artifactId>
    <version>1.2</version>
  </dependency>

commons-cli-1.2.jar is not visible to your code.

http://commons.apache.org/proper/commons-lang/ states the following:

Note that Lang 3.0 (and subsequent versions) use a different package (org.apache.commons.lang3) than the previous versions (org.apache.commons.lang), allowing it to be used at the same time as an earlier version.

So change the package accordingly, or heed Richard Tingle's advice and left click the error+light bulb icon in the gutter (were line numbers are shown) and choose "Add import for...".

import org.apache.commons.lang3.StringUtils;