Apache Commons Math'SummaryStatistics无法解析为类型'

Question

I am attempting to use Apache Commons Math 3.3 for a static data processing class, and am using Eclipse Mars to create it. I have successfully downloaded the bin and src files, and added them to the build path of my project; I can see them in my JRE System Library. I have also added the javadoc URL in the 'Javadoc Location' tab. I am successful in importing classes from the library.

However, when I attempt to instantiate an object from AC-M, Eclipse is unable to resolve that object as a type. For instance,

import org.apache.commons.math3.stat.descriptive.SummaryStatistics.*;

public class Stats {

public static double mean(double[] data) {
    SummaryStatistics curr = new SummaryStatistics();
    for (int a = 0; a < data.length; a++) {
        curr.addValue(data[a]);
    }
    double mn = curr.getMean();
    return mn;}

}

The import statement works fine. However, immediately Eclipse reads an error in my 4th line of code:

SummaryStatistics cannot be resolved to a type

This occurs for all other objects, eg PearsonsCorrelation , SimpleRegression , etc. (I successfully import the respective portions of the library for all objects.) Eclipse offers an option to 'Fix project setup..', yet upon clicking, no solutions are available. I have cleaned the buildpath to no avail. I would appreciate assistance in fixing this problem.

EDIT: I added the jar files by selecting the package of interest and clicking Properties>JRE System Library [jre8] Edit...>Installed JREs...>Edit...>Add External JARs...then adding commons-math3-3.3.jar to the library.

Answer 1

This import:

import org.apache.commons.math3.stat.descriptive.SummaryStatistics.*;

doesn't import SummaryStatistics itself, just any classes defined within that class. Add:

import org.apache.commons.math3.stat.descriptive.SummaryStatistics;

as well.

Answer 2

It was caused by the fact that Eclipse environment was set not to build automatically (Project -> Build Automatically).

Even though I was adding a correct JARs (through Project - Properties - Java Build Path - Libraries), Eclipse did not rebuild, meaning it didn't recalculate new dependencies (and didn't apply them on the existing source).

https://www.eclipse.org/forums/index.php/t/67910/