ThreadLocal 源码阅读

 val threadLocal= ThreadLocal<任何>()
 threadLocal.set("hhahah")
 threadLocal.get()
<p>public void set(T value) {
Thread t = Thread.currentThread();
ThreadLocalMap map = getMap(t);
if (map != null)
map.set(this, value);
else
createMap(t, value);
}</p>
<p>1.可见是由map中取值，如果getMap(t)存在则直接set，否者则创建</p>
<p>ThreadLocalMap getMap(Thread t) {
return t.threadLocals;
}</p>
<p>2.getmap() 是从当前线程中取出自己的 ThreadLocalMap</p>
<p>void createMap(Thread t, T firstValue) {
t.threadLocals = new ThreadLocalMap(this, firstValue);
}</p>
<p>ThreadLocalMap(ThreadLocal<?> firstKey, Object firstValue) {
table = new Entry[INITIAL_CAPACITY];
int i = firstKey.threadLocalHashCode & (INITIAL_CAPACITY - 1);
table[i] = new Entry(firstKey, firstValue);
size = 1;
setThreshold(INITIAL_CAPACITY);
}</p>
<p>3.可知ThreadLocalMap里面是一个散列表，下标是ThreadLocal， 值是set里面的value</p>
<p>4.至此set跟踪完毕，由此可知， ThreadLocal的set实际上是，
初始化了当前线程的threadLocals，并且把值通过散列表存入自己内部</p>
<p>5.每一个ThreadLocal  都是线程里面散列表的下标