Java中没有CuncurrentSkipListMap的线程安全方法 [英] Not thread safe methods of CuncurrentSkipListMap in Java

问题描述

在我的Java项目中，我需要以多线程的方式使用TreeMap。我发现ConcurrentSkipListMap是我需要的，但有些方法不是线程安全的。其中之一 - containsKey（对象键）。以多种方式使用此方法的典型解决方案是什么？在我的程序中，我需要放置不会取代旧的密钥，如果不可能，我将放入另一个密钥而不会获得唯一密钥。应该使用什么构造而不是包含键，因为我不能丢失信息？

In my Java project I need to use TreeMap in multihreaded way. I found that ConcurrentSkipListMap is what that I need but some methods are not thread safe. One of them - containsKey(Object key). What is a typical solution for using this methods in multhreded way? In my program I need put key that will not replace old and if it's impossible I will be putting another key while will not get unique key. What construction should use instead containsKey as i can't lost information?

推荐答案

如果你担心containsKey结果在你面前陈旧可以采取行动，或关于此警告javadoc ：

If you are worried about containsKey results going stale before you can act on them, or about this warning in the javadoc:

此外，不保证以原子方式执行批量操作putAll，equals，toArray，containsValue和clear 。例如，与putAll操作同时运行的迭代器可能只查看一些添加的元素。

Additionally, the bulk operations putAll, equals, toArray, containsValue, and clear are not guaranteed to be performed atomically. For example, an iterator operating concurrently with a putAll operation might view only some of the added elements.

您可以使用ConcurrentSkipListMap上定义的方法。例如，请参阅 putIfAbsent ：

there are methods defined on ConcurrentSkipListMap that you can use instead. For instance, see putIfAbsent:

如果指定的键尚未与值关联，请将其与给定值相关联。这相当于

If the specified key is not already associated with a value, associate it with the given value. This is equivalent to

if (!map.containsKey(key))
    return map.put(key, value);
else
    return map.get(key);

除了动作以原子方式执行。

except that the action is performed atomically.

另请参阅删除和替换方法。

Also see the methods remove and replace.

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