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:
- open project properties
- choose Java Build Path
- tab to Libraries
- add jars (if the jar is inside your project folder)
- 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
Download apache-lang common from apache jakarta sie:
http://commons.apache.org/lang/
After getting jar file please put this jar in your project's build path, if you are not able to find build path then go Jdeveloper help file and type "build path" and you will get all intrustion over there.
Download commons-lang and throw it into your /WEB-INF/lib folder.
If its not a web application you have to check how you can add it to your build path with JDeveloper.
Detailed steps -
0) Download commons-lang-2.5-bin.zip from Apache Commons - Lang Downloads http://commons.apache.org/lang/download_lang.cgi Expand the archive in a directory (eg. \projects\commons-lang-2.5)
In Eclipse -
1). Put the library in the Java build path
Eclipse -> Preferences: Java - Build path - User Libraries push the "New..." button, and in the "User library name:" enter 'appache-commons-lang'.
Click to select "appache-commons-lang" in the "Defined user libraries" list and then click on the "Add JARs..." button and browse for commons-lang-2.5.jar (in the folder saved earlier) and select it.
In the "Defined user libraries", under commons-lang-2.5.jar need to have "Source attachment" and "Javadoc location" specified. For each of them, select it, then push "Edit..." , then "External file" and browse for the corresponding jar (commons-lang-2.5-sources.jar and commons-lang-2.5-javadoc.jar)
2) In the project add this user library In the Package Explorer right-click on the project name, go to Properties, and select the Libraries tab; click the "Add Library..." button, from the list select "User library" , "Next", mark [x] appache-commons-lang, and click "Finish"
You could create a User Library using Apache Commons Lang in Eclipse. User library is a set of jars (these jars can be stored wherever you like). Once defined, user library can be reused in various projects.
You can find more information how to do this for example here (in an accepted answer).
After creating a user library you can add it to your projects just as any other library (Project Properties -> Java Build Path -> Libraries -> Add library -> User library -> Next -> choose your library).