From the project's main directory (wherever the project's pom.xml lives), run:

mvn package

This will compile, run tests, and package the project with its dependencies into the target subdirectory.

Once the package is done, you can run the program with:

java -jar target/FTPClient-1.0-SNAPSHOT.jar

and follow it up with any command-line args you'd like to run it with. Here are the current args for command-line usage:

usage: FTPClient
 -c,--copy <PATHS>           Copy a directory on the server.
 -C,--connect <SERVER>       Begin or switch the connection context.
 -d,--delete <PATH>          Delete a file, use with -R for a directory.
 -g,--get <PATHS>            Get file(s).
 -h,--help                   Print this help information.
 -i,--dir <PATH>             Create a directory.
 -l,--list <PATH>            List files and directories.
 -L,--local                  Source is the local machine.
 -m,--modify <OCTAL, PATH>   Modify a file's permissions on the server.
 -N,--disconnect             Disconnect from the current connection
                             context.
 -p,--put <PATHS>            Put file(s).
 -R,--recursive              Where allowed, target is a directory.

It may be a good idea to clean between packages if you're switching between branches frequently. From the project's main directory, run:

mvn clean

to remove any old artifacts from previous builds. This typically removes the target subdirectory and its contents.

If you'd like to generate all sorts of Javadocs, test results, and other documentation for the project, run:

mvn site

and a website containing all documentation relevant to the project will be created in the target/site subdirectory, with the root at index.html.