package org.apache.commons does not exist

Question

I'd love to use EnumeratedIntegerDistribution() from org.apache.commons.math3.distribution, to get discrete probabilities distribution

int[] nums_to_generate          = new int[]    { -1,   1,    0  };
double[] discrete_probabilities = new double[] { 0.4, 0.4, 0.2  };

I'm working wiht jdk7 , on windows Xp, running from Command Line

I do:

• add to my source file

  import org.apache.commons.math3; 
  

• download commons-math3-3.2 and unpackage it to my current folder

• compile my source with the classpath: (either)

  javac -cp ./commons-math3-3.2/commons-math3-3.2.jar:. ConflictsAnimation.java
  javac -cp   commons-math3-3.2/commons-math3-3.2.jar   ConflictsAnimation.java
  

Still I've got a mysterious

    "error: package org.apache.commons does not exist"

Who knows what happens ? I really need a help.

Note:

compilation (and run) is OK without the classpath and without the import of "apache" and call to numeratedIntegerDistribution().

compilation with the classpath and without the "appache"s give nonsense errors.

Thanks a lot in advance for your great skills, the programmers!

---

Here is short demonstration:

import java.lang.Math.*;
import org.apache.commons.math3;

public class CheckMe {

    public CheckMe() {

        System.out.println("let us check it out"); 
        System.out.println(generate_rand_distribution (10));
    }

    private static int[] generate_rand_distribution (int count){
    int[] nums_to_generate          = new int[]    { -1,   1,    0  };
        double[] discrete_probabilities = new double[] { 0.4, 0.4, 0.2  };
    int[] samples = null;

        EnumeratedIntegerDistribution distribution = 
        new EnumeratedIntegerDistribution(nums_to_generate, discrete_probabilities);

        samples = distribution.sample (count);

    return (samples);
    }   

    public static void main (String args[]) { 
        System.out.println("Main: ");
        CheckMe  animation = new CheckMe();  
    } 
}

Solution

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.

Comments

[Jon Skeet]

What exactly are these "nonsense errors"? Can you show a short but complete program demonstrating the problem?

[Dave Newton]

You can't just import a package, you need to import actual classes. You'll need to provide more information for help, though, like where the jar and your classes are located etc.

[Galia]

commons-math3-3.2 is located in my current folder together with my source file. I'm adding a short program having the same problem.

[Dave Newton]

If it's in your current folder then why are you giving it a path to the jar file?

[Galia]

Hi Jon, the compilation was fin, however this apache might be not found at run what seems to cause class not found exception. stackoverflow.com/questions/20954322/… Thanks you for anything.

[Jon Skeet]

@Galia: Yes, as per the answer there you need the jar file on the classpath when running it, too.

[Galia]

yes it resolved the problem. But created somehow another one: any of my java executables if I run them now (which are not using apache) fail with the error of not finding the principle class. Nether restarting nor using "." as -cp argument didin't change this. May it be connected to the fact that I have got now Sdk and Jdk, though Before runnig with clathpass flag this did no problem to my other java exectutables.

[PhoneixS]

If the problem is other, create a new question. And if this answer answer the original question mark it as accepted.