Console APP - Call function based upon a command line parameter

Question

I am writing an extrensible console ( interactive console ) application was thinking having my application read in the command, then look up which function to use to process its parameters.
say the command the user types is "print Hello World"
I would just grab the first parameter, recognize it as the print command , and then call a function in my class that prints out "Hello World" to the screen.
Instead of doing a bunch of If statement to match the first argument to a recognized command, what I would like to do is have a type of Hash table that points to the correct function to process the command.
So.. something like :
String cmd = console.readline( "Enter your command" ); - get the users command
"function = HashMap.get( cmd)" - get the function out of the hashmap
"function( parameters )" - run the function
the prompt for another command, as long as the last command wasn't "exit"
I would have to check to make sure the command had a function mapped to it, but with this setup, all I do is update the table when I need to add a new command. and the function( method ) that processes it.
Thanks!

Answer 1

It sounds like you're describing the Command pattern. It normally goes something like this:
interface Command {
    Object execute(String... args);
Map<String, Command> commands = new HashMap<String,Command>();
commands.put("print", new Command() {
    public Object execute(String... args) {
        System.out.print(args);
// ... and more commands
//.. then in your command-line UI, for example:
BufferedReader in = new BufferedReader...
String line;
while((line = in.readLine()) != null) {
    String[] tokens = line.split();
    Command cmd = commands.get(tokens[0]);
    String[] args = take_subarray_of_tokens_starting_at_1_I_forget_easiest_way_to_do_that(tokens);
    Object returnval = cmd.execute(args);
    // maybe you'll want to do something with return val, or maybe it should be an int more like an exit val, whatever
}Not tested but you get the idea.