Scala REPL FAQ: How do I add a Jar file to the Scala REPL classpath? (The Scala REPL is the interactive command line you get if you just type "scala" at your command line.)
To add a new jar file to the Scala REPL classpath (interactive command line classpath), use the ":cp" command at the command line, like this:
scala> :cp myjar.jar
After you do this, you should see a reply from the REPL like this:
Added '/Users/Al/tests/myjar.jar'. Your new classpath is: ".:/Users/Al/tests/myjar.jar"
At this time you can begin using the classes in your jar (though you'll have to import them, as usual).
I usually find that I need to add a jar file to the Scala REPL after I've been running the REPL, but if you happen to know that you're going to need to add a jar file to the classpath when you start the interpreter, you can do so like this:
$ scala -cp junit-4.8.1.jar
As you can see, this approach uses the usual "-cp" classpath option that is used by the scalac and javac commands.
I learned about the Scala REPL ":cp" command by looking at the "help" from within the REPL. Here's what that help looks like with my current version of Scala, version 2.9.1:
scala> :help All commands can be abbreviated, e.g. :he instead of :help. Those marked with a * have more detailed help, e.g. :help imports. :cp <path> add a jar or directory to the classpath :help [command] print this summary or command-specific help :history [num] show the history (optional num is commands to show) :h? <string> search the history :imports [name name ...] show import history, identifying sources of names :implicits [-v] show the implicits in scope :javap <path|class> disassemble a file or class name :keybindings show how ctrl-[A-Z] and other keys are bound :load <path> load and interpret a Scala file :paste enter paste mode: all input up to ctrl-D compiled together :power enable power user mode :quit exit the interpreter :replay reset execution and replay all previous commands :sh <command line> run a shell command (result is implicitly => List[String]) :silent disable/enable automatic printing of results :type <expr> display the type of an expression without evaluating it