[英]Iterator, ListIterator and List
I have encountered a problem that I cannot quite figure out. 我遇到了一个我无法完全解决的问题。 Would be super if you guys could help me out =)
如果你们可以帮助我,那就太好了=)
I have a Lobby.Class that has a draw() Method: 我有一个具有draw()方法的Lobby.Class:
public void draw() {
//USE ITERATOR TO DRAW
Iterator<Player> itr = players.iterator();
while(itr.hasNext()) {
Player player = itr.next();
int off = players.indexOf(player); //THE CORRECT HEIGHT
player.draw(off);
}
}
Note that this is a server/client game 请注意,这是服务器/客户端游戏
The Lobby.Class has also 1 method called addPlayer() Lobby.Class也有一种称为addPlayer()的方法
public void addPlayer(String _playerName, String _class, String _string_id) {
int _id = Integer.parseInt(_string_id);
//CREATE THE NEW PLAYER
Player new_player = new Player(x, y, _id, _playerName, _class);
//IF THIS PLAYER IS ME
if(new_player.getID() == id) {
me = new_player;
} else {
//TELL THE NEW PLAYER I EXIST
ClientValue.getClient().iExist(_id);
//THIS WILL SEND TO CLIENT THAT WILL SEND TO THE SERVER
//THAT WILL LOOK FOR THE ID AND SEND TO CLIENT OF THAT ID
//AND THE CLIENT WILL SEND TO LOBBY UPDATE PLAYERS()
}
players.add(new_player);
chat.appendChat(chat.joinString(_playerName, _class));
}
The Lobby.Class has also 1 method called updatePlayers() Lobby.Class也有1个称为updatePlayers()的方法
public void updatePlayers(String _playerName, String _class, String _string_id) {
//THIS IS CALLED WHEN THE SERVER TELLS THIS PLAYER
//ABOUT OTHER PLAYERS
int _id = Integer.parseInt(_string_id);
//CREATE THE NEW PLAYER
Player new_player = new Player(x, y, _id, _playerName, _class);
players.add(new_player);
}
Now my problem is the players List, when I enter the lobby addPlayer()
will Run at the same time when 2 players join, or when the updatePlayers()
are run with addPlayer()
现在我的问题是球员名单,当我进入大厅
addPlayer()
将在同一时间运行在2个玩家加入,或者当updatePlayers()
与运行addPlayer()
The Exception i get is: ConcurrentModificationException 我得到的异常是: ConcurrentModificationException
I am missing two methods, 1 for adding players with an Iterator if possible, 1 for removing players . 我缺少两种方法,一种是在可能的情况下使用迭代器添加播放器,另一种是删除播放器 。 So that I wont get the error for modifying the players List while going trough it or adding/removing it.
这样我就不会在通过或添加/删除播放器列表时收到修改播放器列表的错误。
I have tried puzzling around with Iteror and ListIterator, but as I have never used them before, I am not sure what to do. 我曾尝试过弄乱Iteror和ListIterator,但由于我以前从未使用过它们,因此我不确定该怎么做。 I need some advice on how to do this.
我需要一些有关如何执行此操作的建议。 Many thanks in advance =)
提前非常感谢=)
Solution: 解:
private List<Player> players = Collections.synchronizedList(new ArrayList<Player>());
public synchronized void playersList(String cmd, Player _player) {
Iterator<Player> itr = players.iterator();
if(cmd.equals("draw")) {
while(itr.hasNext()) {
Player player = itr.next();
int off = players.indexOf(player);
player.draw(off);
}
} else if(cmd.equals("add")) {
players.add(_player);
} else if(cmd.equals("remove")) {
players.remove(_player);
}
}
You need to synchronise access to the list, allowing only one thread to access the list at a time. 您需要同步对列表的访问,一次只允许一个线程访问列表。
You could use a synchronized
block around each access point (including the entire paint method) or you could wrap the player list in a thread safe list using Collections#synchronizedList
or, instead of an iterator, you could use the toArray
method of players 您可以在每个访问点周围使用
synchronized
块(包括整个paint方法),也可以使用Collections#synchronizedList
将播放器列表包装在线程安全列表中,或者可以使用播放器的toArray
方法来代替迭代器
Player[] arrayOfPlayers = players.toArray(new Player[players.size()]);
You are still going to synchronized
the this call, but your only locking one line, not a whole loop 您仍将
synchronized
此调用,但是您只能锁定一行,而不是整个循环
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