Need help understanding communicating with a thread

Question

I am trying to write a library of a MUD engine that runs in its separate thread, but I am new to Java and not sure I have the concepts right. The heart of it is a class called Game, that implements the Runnable Interface and has 2 key methods - void DoCommand(String command) and String GetUpdates(String lastUpdate).
* The Run() method runs an infinite loop that processes queued commands when they are due, and pauses (wait() or sleep()) in between. The results are queued in an update list.
* The DoCommand() method queues commands to be processed in Run().
* The GetUpdates() method pulls updates from the update list one at a time.
Will there be a problem if DoCommand() or GetUpdates() are called while Run() is paused or running?
How do I get DoCommand() to wake Run() when a new command is received?
BTW: I am new to Java so please make the answers simple enough for me to understand.
My theoretical code skeleton is below, but I am not confident in it given these questions I have.
* To change this template, choose Tools | Templates
* and open the template in the editor.
package me.org.prototype;
import java.util.ArrayList;
/** Definition of the game engine. The engine runs in its own threat, updating
* and maintaining its state, objects, etc. IO is handled through a separate
* interface (GUI or something else) that communicates with this object. NOTE:
* this interface is the game interface and not a Java interface.
* <P> Usage create a Game instance and a place it in a thread. Once started you
* can pass in input via the DoCommand(...) method, and get updates from its
* GetUpdates(...) method. To exit interrupt the thread or call
* DoCommand("quit");
* @author atbudd
public class Game implements Runnable {
    /** Next time (computer time) that a game action is to be run. Use 0 to
     * indicate no action pending.
    int nextRunTime = 0;
    /** Boolean indicating running state of game. */
    boolean gameRunning = true;
    /** List of game updates. */
    ArrayList<String> updateList = new ArrayList<String>();
    /** Perform's game's main loop. */
    public void run() {
        // Main loop code.
        while (gameRunning) {
            // Process game objects and pending actions.
            try {
                // Pause until next action due.
                if (nextRunTime > 0) {
                    wait(nextRunTime - System.nanoTime());
                } // Otherwise wait until action specified. NOTE: action specified elsewhere.
                else {
                    wait();
            } catch (InterruptedException exception) {
                // If quit command received...
                if (exception.getMessage().equalsIgnoreCase("quit")) {
                    gameRunning = false;
                /* Otherwise new command received. wait(...)interrupted and loop
                 * resumed so that nextRunTime can be updated to when new
                 * command due.
    /** Peforms specified command.
     * @param command Command to be processed.
    public void DoCommand(String command) throws InterruptedException {
        // Process command.
        if (command.equalsIgnoreCase("quit")) {
            // Interrupt game with exit interrupt.
            throw new InterruptedException(command);
        else if ((nextRunTime == 0) /* || command due before nextRunTime */) {
            // Add command to a processing queue.
            // Interrupt game to schedule / process command.
            throw new InterruptedException("new command");
    /** Returns updates since update specified.
     * @param lastUpdate Last update received from game. Use "" if not updates
     * received yet.
    public String GetUpdates(String lastUpdate) {
        // Update string
        String updateString = null;
        /* (TODO) Get updates from update list that come after last update and
         * place in update string.
        // Return update string.
        return updateString;
}

Answer 1

Furrage wrote:
OK cotton.m. I will try that and see what happens.
What about my question about which thread DoCommand() will run in (my second post in this message thread)? Any answers? I think that's key to me understanding what is needed to get my code to work the way I want, but I don't know how to test which thread it is running in.Possibly by interrupt.
Or possibly by adding the command to a command queue which in turn would notify a thread waiting on the queue for the next command.