Java 同步块与 Collections.synchronizedMap
以下代码是否设置为正确同步 synchronizedMap 上的调用?
Is the following code set up to correctly synchronize the calls on synchronizedMap?
public class MyClass {
private static Map<String, List<String>> synchronizedMap = Collections.synchronizedMap(new HashMap<String, List<String>>());
public void doWork(String key) {
List<String> values = null;
while ((values = synchronizedMap.remove(key)) != null) {
//do something with values
}
}
public static void addToMap(String key, String value) {
synchronized (synchronizedMap) {
if (synchronizedMap.containsKey(key)) {
synchronizedMap.get(key).add(value);
}
else {
List<String> valuesList = new ArrayList<String>();
valuesList.add(value);
synchronizedMap.put(key, valuesList);
}
}
}
}
据我了解,我需要 addToMap() 中的同步块来防止另一个线程调用 remove() 或 containsKey()在我完成对 put() 的调用之前,但我不需要 doWork() 中的同步块,因为另一个线程无法进入 addToMap() 在 remove() 返回之前,因为我最初使用 Collections.synchronizedMap() 创建了地图.那是对的吗?有没有更好的方法来做到这一点?
From my understanding, I need the synchronized block in addToMap() to prevent another thread from calling remove() or containsKey() before I get through the call to put() but I do not need a synchronized block in doWork() because another thread cannot enter the synchronized block in addToMap() before remove() returns because I created the Map originally with Collections.synchronizedMap(). Is that correct? Is there a better way to do this?
推荐答案
Collections.synchronizedMap() 保证你想在地图上运行的每个原子操作都会被同步.
Collections.synchronizedMap() guarantees that each atomic operation you want to run on the map will be synchronized.
但是,在地图上运行两个(或更多)操作必须在一个块中同步.所以是的 - 你正在正确同步.
Running two (or more) operations on the map however, must be synchronized in a block. So yes - you are synchronizing correctly.
相关文章