ThreadLocal解析

ThreadLocal 是java.lang 包下的一个类。

前提：ThreadLocal里面有一个静态内部类 ThreadLocalMap 

先看get方法 

   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();
    }

 得到当前线程对象，getMap（）方法是得到当前线程对象的ThreadLocalMap对象（Thread类也有ThreadMap这个属性）

   /* ThreadLocal values pertaining to this thread. This map is maintained
     * by the ThreadLocal class. */
    ThreadLocal.ThreadLocalMap threadLocals = null;

    private Entry getEntry(ThreadLocal key) {
            int i = key.threadLocalHashCode & (table.length - 1);
            Entry e = table[i];
            if (e != null && e.get() == key)
                return e;
            else
                return getEntryAfterMiss(key, i, e);
        }

一句话总结：ThreadLocal 得到当前线程的ThreadLocalMap属性，然后对这个属性进行读取，写入和删除操作；