並發修改異常

Question

我的以下代碼引發並發修改異常，但我無法解決。 救命！

  {
    long now = new Date().getTime();
    Set<String> keyset = requests.keySet();
    Iterator<String> iterator = keyset.iterator();

    while (iterator.hasNext()) {
        String packetId = iterator.next();
        RequestHolder entry = requests.get(packetId);
        if (entry.isExpired(now)) {
            entry.getListener().onTimeout(packetId);
            iterator.remove();
        }
    }
  }

Answer 1

替換為

long now = new Date().getTime();
Iterator<Map.Entry<String, RequestHolder>> iterator = requests.entrySet().iterator();

while (iterator.hasNext()) {
    Map.Entry<String, RequestHolder> entry = iterator.next();
    String packetId = entry.getKey();
    RequestHolder requestHolder = entry.getValue();
    if (requestHolder.isExpired(now)) {
        requestHolder.getListener().onTimeout(packetId);
        iterator.remove();
    }
}

解決方案是遍歷整個集合而不是遍歷密鑰集，使用密鑰集迭代器再次訪問集合中的條目，並從密鑰集中刪除條目

Answer 2

用這個替換您的while循環...

for (Entry<String, RequestHolder> entryElem : requests.keySet()) {
            String packetId = entryElem.getValue();
        RequestHolder entry = requests.getValue.get(packetId);
        if (entry.isExpired(now)) {
            entry.getListener().onTimeout(packetId);
            iterator.remove();
        }
    }