带你读《2022技术人的百宝黑皮书》——合理使用线程池以及线程变量（11）

/**
*Sets the current thread's copy of this thread-local variable
*to the specified value. Most subclasses will have no need to
*override this method, relying solely on the {@link #initialValue}
*method to set the values of thread-locals.
*
*@param value the value to be stored in the current thread's copy of
* this thread-local.
*/
public void set(T value) {
// 1. 获取当前线程
Thread t = Thread.currentThread();
// 2. 获取当前线程内部的ThreadLocalMap变量ThreadLocalMap map = getMap(t);
if (map != null)
// 3. 设 置 value map.set(this, value);
else
// 4. 若map为null则创建ThreadLocalMap createMap(t, value);
}

static class ThreadLocalMap {
/**
*The entries in this hash map extend WeakReference, using
*its main ref field as the key (which is always a
*ThreadLocal object). Note that null keys (i.e. entry.get()
* == null) mean that the key is no longer referenced, so the
*entry can be expunged from table. Such entries are referred to
*as "stale entries" in the code that follows.