gistfile1.txt

import java.io.Console;

interface Context {
	State state();

	void state(State state);

	Console console();
}

interface State {
	boolean process(Context ctx);
}

enum CommandLineStates implements State {
	LOGIN {
		public final boolean process(Context ctx) {
			System.out.print("enter password:");
			char[] password = ctx.console().readPassword();
			for (int i = 0; i < password.length; i++) {
				if (PASSWORD[i] != password[i]) {
					return false;
				}
			}
			ctx.state(ECHO);
			return true;
		}

	},
	ECHO {

		@Override
		public final boolean process(Context ctx) {
			String a = ctx.console().readLine();
			if (a == null) {
				return false;
			}
			System.out.println(a);
			return true;
		}

	};

	private final static char[] PASSWORD = { 'a', 'r', 'i', 'a', 'n' };
}

final class CommandLineContext implements Context {
	private State state;
	private final Console console;

	public CommandLineContext() {
		this.state = CommandLineStates.LOGIN;
		this.console = System.console();
	}

	@Override
	public final State state() {
		return state;
	}

	@Override
	public final void state(State state) {
		this.state = state;
	}

	@Override
	public final Console console() {
		return console;
	}

}

public final class CommandLine {
	private final Context context;

	public CommandLine() {
		this.context = new CommandLineContext();
	}

	public final void run() {
		while (context.state().process(context))
			;
	}

	public static final void main(final String[] args) {
		new CommandLine().run();
	}
}