How to use org.apache.commons.lang namespace in Java?

I tried in Eclipse to use org.apache.commons.lang.NotImplementedException, though it seems from what I can see both from IntelliSense and the Package Explorer, that that namespace does not exist.

So I guess I开发者_如何学Go must load some other package(do you call them libraries in java?) than those it loaded by default.

This is my current setup: (link dead)

Download the commons lang library and add it to your eclipse project library.

EDIT (2016/02) : it seems that nowadays the .jar files are not provided as is. You have to get the "binary" archive (e.g. "commons-lang3-3.4-bin.zip") from the same download page and extract it. The required jar files are inside the extracted folder.

To add the jar to your eclipse project library:

1. open project properties
2. choose Java Build Path
3. tab to Libraries
4. add jars (if the jar is inside your project folder)
5. add external jar (if the jar is outside your project folder)

You need to add Apache commons jar file to the project. You can select the jar you want from here - http://commons.apache.org/downloads/index.html
for lang you need this - commons-lang-2.5.jar