public static void main(String[] args) {
   IntStream.range(1, 5).forEach(i -> new Thread(() -> {
       // 設(shè)置線程中本地變量的值
       threadLocal.set("thread-" + i);
       // 打印當(dāng)前線程中本地內(nèi)存中本地變量的值
       System.out.println(threadLocal.get());
       // 清除本地內(nèi)存中的本地變量
       threadLocal.remove();
       // 打印本地變量
       System.out.println("thread-" + i + " after remove: " + threadLocal.get());
   }).start());
}
/*
thread-1
thread-4
thread-4 after remove: null
thread-2
thread-3
thread-2 after remove: null
thread-1 after remove: null
thread-3 after remove: null
*/

public void set(T value) {
    // 獲取當(dāng)前線程
    Thread t = Thread.currentThread();
    // 通過(guò)當(dāng)前線程獲取線程中的ThreadLocal.ThreadLocalMap對(duì)象
    ThreadLocalMap map = getMap(t);
    if (map != null)
        // map不為空，則直接賦值
        map.set(this, value);
    else
        // map為空，則創(chuàng)建一個(gè)ThreadLocalMap對(duì)象
        createMap(t, value);
}
// 根據(jù)提供的線程對(duì)象，和指定的值，創(chuàng)建一個(gè)ThreadLocalMap對(duì)象
void createMap(Thread t, T firstValue) {
    t.threadLocals = new ThreadLocalMap(this, firstValue);
}
// threadLocals是Thread類的一個(gè)屬性
ThreadLocalMap getMap(Thread t) {
    return t.threadLocals;
}
/*
Thread 類 182行
	// ThreadLocal values pertaining to this thread. This map is maintained by the ThreadLocal class.
    ThreadLocal.ThreadLocalMap threadLocals = null;
*/

// ThreadLocalMap中的內(nèi)部類，存放key，value
static class Entry extends WeakReference<ThreadLocal<?>> {
    // 與此ThreadLocal關(guān)聯(lián)的值
    Object value;
	// k：ThreadLocal的引用，被傳遞給WeakReference的構(gòu)造方法
    Entry(ThreadLocal<?> k, Object v) {
        super(k);
        value = v;
    }
}
public T get() {
    // 獲取當(dāng)前線程
    Thread t = Thread.currentThread();
    // 通過(guò)當(dāng)前線程獲取線程中的ThreadLocal.ThreadLocalMap對(duì)象
    ThreadLocalMap map = getMap(t);
    if (map != null) {
        // map不為空，通過(guò)this(當(dāng)前對(duì)象，即ThreadLocal對(duì)象)獲取Entry對(duì)象
        ThreadLocalMap.Entry e = map.getEntry(this);
        if (e != null) {
            @SuppressWarnings("unchecked")
            T result = (T)e.value;
            // Entry不為空，則直接返回Entry中的value值
            return result;
        }
    }
    // 如果map或Entry為空，則返回初始值-null
    return setInitialValue();
}
// 設(shè)置初始值，初始化ThreadLocalMap對(duì)象，并設(shè)置value為 null
private T setInitialValue() {
    // 初始化值，此方法返回 null
    T value = initialValue();
    Thread t = Thread.currentThread();
    ThreadLocalMap map = getMap(t);
    if (map != null)
        map.set(this, value);
    else
        createMap(t, value);
    return value;
}

public void remove() {
    // 通過(guò)當(dāng)前線程獲取線程中的ThreadLocal.ThreadLocalMap對(duì)象
    ThreadLocalMap m = getMap(Thread.currentThread());
    if (m != null)
        // 移除對(duì)象
        m.remove(this);
}
// 根據(jù)key，刪除對(duì)應(yīng)的所有值
private void remove(ThreadLocal<?> key) {
    Entry[] tab = table;
    int len = tab.length;
    // 獲取key對(duì)應(yīng)的 Entry[] 下標(biāo)
    int i = key.threadLocalHashCode & (len-1);
    for (Entry e = tab[i];
         e != null;
         // 獲取下一個(gè)Entry對(duì)象
         e = tab[i = nextIndex(i, len)]) {
        if (e.get() == key) {
            e.clear();
            // 通過(guò)重新哈希位于staleSlot和下一個(gè)null插槽之間的任何可能沖突的條目，來(lái)清除陳舊的條目。這還會(huì)清除尾隨null之前遇到的所有其他過(guò)時(shí)的條目，防止出現(xiàn)內(nèi)存泄漏問(wèn)題
            expungeStaleEntry(i);
            return;
        }
    }
}