Thread: import class from .jar file

Hello everybody,

I have a few questions regarding how to use a .class file I unpacked from a .jar file I downloaded from the Internet.

I downloaded the commons-io-2.4.jar file from commons . apache . org /proper/commons-io/

In it you can see that there is a class called FileUtil.class:

jar tf commons-io-2.4.jar | grep FileUtil
org/apache/commons/io/FileUtils.class

I extracted this with the following command:

jar xf commons-io-2.4.jar FileUtils.class

It is now in ..uk/ac/ebi/bioinvindex/services/datasearch/commons/FileUtils.class

Now, I have a java file where I would like to use FileUtils.

How do I do that? How do I import it?

Thanks, Matthew

Welcome to the Forum! Please read this topic to learn how to post code correctly and other useful tips for newcomers.

A typical approach is to place the .jar file somewhere on the CLASSPATH (I have a folder for just for 3rd party .jar files) and then just import the desired components as you would any other import. .class files in those packages often have their own imports/dependencies on other pieces of the .jar file, so that if you separate the one file you think you need, you may find you'll have other broken imports if the whole .jar file is not on the CLASSPATH. It's easier to leave the .jar file together than taking it apart and having to manage the pieces.

Okay, so you mean I don't have to extract any vlass files, just leave the original jar file anywhere on CLASSPATH.
How should I write the import ... ; line in my Java code?
Thanks for your quick reply.
Matt

--- Update ---

Never mind, I figured it out!

Good job!

What I was going to say (for the benefit of anyone else with the same question) is to follow the path you used to find and extract the desired .class file and put that in an import statement, something like:

import org.apache.commons.ftp.FTPClient;

imports the FTPClient.class file from the org.apache.commons .jar file.