从ThreadLocal的get和set方法入手
public void set(T value) {
Thread t = Thread.currentThread();
ThreadLocalMap map = getMap(t);
if (map != null)
map.set(this, value);
else
createMap(t, value);
}
public T get() {
Thread t = Thread.currentThread();
ThreadLocalMap map = getMap(t);
if (map != null) {
ThreadLocalMap.Entry e = map.getEntry(this);
if (e != null) {
@SuppressWarnings("unchecked")
T result = (T)e.value;
return result;
}
}
return setInitialValue();
}
ThreadLocalMap getMap(Thread t) {
return t.threadLocals;
}
class Thread implements Runnable {
/* ThreadLocal values pertaining to this thread. This map is maintained
* by the ThreadLocal class. */
ThreadLocal.ThreadLocalMap threadLocals = null;
/*
* InheritableThreadLocal values pertaining to this thread. This map is
* maintained by the InheritableThreadLocal class.
*/
ThreadLocal.ThreadLocalMap inheritableThreadLocals = null;
void createMap(Thread t, T firstValue) {
t.threadLocals = new ThreadLocalMap(this, firstValue);
}
可以看到在set方法中首先会使用getMap方法得到一个ThreadLocalMap，如果map为空就进行初始化调用createMap方法，不为空就网map里面添加数据。所以ThreadLocal里面是靠ThreadLocalMap储存数据的。
get方法也是用ThreadLocalMap里面的方法。