程序完全不能运行。。。

[bileebilee]

编了下面这个程序，是一个Nim游戏，要求可以添加删除重置用户，可是写完之后完全不能运行，我对多个class的程序不是很熟，实在找不出来是怎么回事了，希望各位大神帮帮忙，马上就要交作业了，很急。。。

import java.util.Arrays;

public class NimPlayer {
	
	public String username;
	public String family_name;
	public String given_name;
	public int game;
	public int win;
	public int percentage;
	
	public final static int MAX_PLAYER_NUM = 100;
	static NimPlayer [] players = new NimPlayer[MAX_PLAYER_NUM];
	
	static int numofplayer = 0;
	
	public void addplayer(String username, String family_name, String given_name){
		for (int index = 0; index < numofplayer; index++) {
			if (players[index].username == username) {
				System.out.println("The player already exists.");
				System.out.println();
				System.out.printf(">");
				return;
			}
		}
		players[numofplayer].username = username;
		players[numofplayer].family_name = family_name;
		players[numofplayer].given_name = given_name;
		numofplayer++;
		System.out.println();
		System.out.printf(">");
	}
	
	public void removeplayer(String username){
		for (int index = 0; index < numofplayer; index++) {
			if (players[index].username == username) {
					players[index] = players[numofplayer-1];
					players[numofplayer-1] = null;
					numofplayer--;
					System.out.println();
					System.out.printf(">");
					return;
			}
		}
		System.out.println("The player does not exist.");
		System.out.println();
		System.out.printf(">");
	}
	
	public void removeallplayer(){
		System.out.println("Are you sure you want to remove all players? (y/n)");
		String flag = Nimsys.keyboard.next();
		if (flag == ("y")){
			for (int index = 0; index < numofplayer; index++){
				players[index] = null;
			}
		}
		System.out.println();
		System.out.printf(">");
	}
	
	public void editplayer(String username, String new_family_name, String new_given_name){
		for (int index = 0; index < numofplayer; index++) {
			if (players[index].username == username) {
				players[index].family_name = new_family_name;
				players[index].given_name = new_given_name;
				System.out.println();
				System.out.printf(">");
				return;
				}
		}
		System.out.println("The player does not exist.");
		System.out.println();
		System.out.printf(">");
	}
	
	public void resetstats(String username){
		for (int index = 0; index < numofplayer; index++) {
			if (players[index].username == username) {
				players[index].game = 0;
				players[index].win = 0;
				players[index].percentage = 0;
				System.out.println();
				System.out.printf(">");
				return;
			}
		}
		System.out.println("The player does not exist.");
		System.out.println();
		System.out.printf(">");
	}
	
	public void resetstatsall(){
		System.out.println("Are you sure you want to reset all player statistics? (y/n)");
		String flag = Nimsys.keyboard.next();
		if (flag == ("y")){
			for (int index = 0; index < numofplayer; index++){
				players[index].game = 0;
				players[index].win = 0;
				players[index].percentage = 0;
			}
		}
		System.out.println();
		System.out.printf(">");
	}
	
	public void displayplayer(String username){
		for (int index = 0; index < numofplayer; index++) {
			if (players[index].username == username) {
				System.out.println(getdescription(index));
				System.out.println();
				System.out.printf(">");
				return;
			}
		}
		System.out.println("The player does not exist.");
		System.out.println();
		System.out.printf(">");
	}
	
	public void displayallplayer(){
		Arrays.sort(players);
		for (int index = 0; index < numofplayer; index++){
			System.out.println(getdescription(index));
		}
	}
	
	public static String getdescription(int index){
		String description = (players[index].username + ", " + players[index].given_name + ", " + players[index].family_name + ", " + players[index].game + "games, " + players[index].win + "wins");
		return description;
	}

import java.util.Scanner;

public class Nimsys {
	
	public static Scanner keyboard;
	
	public static void main(String[] args){
		keyboard = new Scanner(System.in);
		System.out.println("Welcome to Nim");
		System.out.printf("\n>");
		NimPlayer player = new NimPlayer();
		NimGame newgame = new NimGame();
		while(true){
			String[] command = keyboard.next().split(",| ");
			
			if (command[0] == "addplayer")
				player.addplayer(command[1], command[2], command[3]);
			else if ((command[0] == "removeplayer") && (command.length != 1))
				player.removeplayer(command[1]);
			else if ((command[0] == "removeplayer") && (command.length == 1))
				player.removeallplayer();
			else if (command[0] == "editplayer")
				player.editplayer(command[1], command[2], command[3]);
			else if ((command[0] == "resetstats") && (command.length != 1))
				player.resetstats(command[1]);
			else if ((command[0] == "resetstats") && (command.length == 1))
				player.resetstatsall();
			else if ((command[0] == "displayplayer") && (command.length != 1))
				player.displayplayer(command[1]);
			else if ((command[0] == "displayplayer") && (command.length == 1))
				player.displayallplayer();
			else if (command[0] == "startgame")
				newgame.startgame(Integer.parseInt(command[1]), Integer.parseInt(command[2]), command[3], command[4]);		
		}	
	}

public class NimGame {
	
	public void startgame(int initialstones, int upperbound, String username1, String username2){
		int currentplayer;
		int nextplayer;
		int removal;
		if (checkplayer(username1) && checkplayer(username2)){
			currentplayer = getplyerindex(username1);
			nextplayer = getplyerindex(username2);
			System.out.println();
			System.out.println("Initial stone count: " + initialstones);
			System.out.println("Maximum stone removal: " + upperbound);
			System.out.println("Player1: " + NimPlayer.players[currentplayer].given_name + NimPlayer.players[currentplayer].family_name);
			System.out.println("Player2: " + NimPlayer.players[nextplayer].given_name + NimPlayer.players[nextplayer].family_name);
		}
		else{
			System.out.println("One of the players does not exist.");
			System.out.println();
			System.out.printf(">");
			return;
		}
		
		while (initialstones != 0)
		{
			System.out.println();
			System.out.printf(initialstones + " stones left:");
			int stone;
			for(stone = initialstones;stone >0;stone--)
				System.out.print(" *");
			System.out.println("\n" + NimPlayer.players[currentplayer].given_name + "'s turn - remove how many?");
			removal = Nimsys.keyboard.nextInt();
			if (removal > 0 && removal < min(initialstones, upperbound)){
				initialstones = initialstones - removal;
				int temp = currentplayer;
				nextplayer = currentplayer;
				currentplayer = temp;
			}
			else{
				System.out.println("/nInvalid move. You must remove  between 1 and " + min(initialstones, upperbound) + "stones.");
				continue;
			}
		}
		System.out.println();
		System.out.println("Game Over");
		System.out.println(NimPlayer.players[currentplayer].given_name + " " + NimPlayer.players[currentplayer].family_name + " wins!");
		NimPlayer.players[currentplayer].game++;
		NimPlayer.players[currentplayer].win++;
		NimPlayer.players[nextplayer].game++;
	}
	
	public static boolean checkplayer(String username){
		for (int index = 0; index < NimPlayer.numofplayer; index++){
			if (NimPlayer.players[index].username == username)
				return true;
		}
		return false;
	}
	
	public static int getplyerindex(String username){
		int playerindex = 0;
		for (int index = 0; index < NimPlayer.numofplayer; index++){
			if (NimPlayer.players[index].username == username)
				playerindex  = index;
		}
		return playerindex;
	}
	
	private static int min(int n1, int n2) {
		int temp = 0;
		if (n1 < n2)
			temp = n1;
		else
			temp = n2;
		return temp;
	}
}

[-江沐风-]

直接运行Nimsys这个类不就可以了；