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修正ThreadLocal造成内存泄漏的描述 #2589

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Snailclimb merged 1 commit into from
Jan 26, 2025
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修正ThreadLocal造成内存泄漏的描述 #2589

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2 changes: 1 addition & 1 deletion docs/java/concurrent/java-concurrent-questions-03.md
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Expand Up @@ -148,7 +148,7 @@ static class Entry extends WeakReference<ThreadLocal<?>> {
- **key 是弱引用**：`ThreadLocalMap` 中的 key 是 `ThreadLocal` 的弱引用 (`WeakReference<ThreadLocal<?>>`)。 这意味着，如果 `ThreadLocal` 实例不再被任何强引用指向，垃圾回收器会在下次 GC 时回收该实例，导致 `ThreadLocalMap` 中对应的 key 变为 `null`。
- **value 是强引用**：即使 `key` 被 GC 回收，`value` 仍然被 `ThreadLocalMap.Entry` 强引用存在，无法被 GC 回收。

当 `ThreadLocal` 实例失去强引用后，其对应的 value 仍然存在于 `ThreadLocalMap` 中，因为 `Entry` 对象强引用了它。如果线程持续存活（例如线程池中的线程），`ThreadLocalMap` 也会一直存在，导致 key 为 `null` 的 entry 无法被垃圾回收，机会造成内存泄漏。
当 `ThreadLocal` 实例失去强引用后，其对应的 value 仍然存在于 `ThreadLocalMap` 中，因为 `Entry` 对象强引用了它。如果线程持续存活（例如线程池中的线程），`ThreadLocalMap` 也会一直存在，导致 key 为 `null` 的 entry 无法被垃圾回收，即会造成内存泄漏。

也就是说，内存泄漏的发生需要同时满足两个条件：

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