Java中的ThreadLocal

static final ThreadLocal sThreadLocal = new ThreadLocal();
sThreadLocal.set()
sThreadLocal.get()

//set 方法
public void set(T value) {
      //获取当前线程
      Thread t = Thread.currentThread();
      //实际存储的数据结构类型
      ThreadLocalMap map = getMap(t);
      //如果存在map就直接set，没有则创建map并set
      if (map != null)
          map.set(this, value);
      else
          createMap(t, value);
  }
  
//getMap方法
ThreadLocalMap getMap(Thread t) {
      //thred中维护了一个ThreadLocalMap
      return t.threadLocals;
 }
 
//createMap
void createMap(Thread t, T firstValue) {
      //实例化一个新的ThreadLocalMap，并赋值给线程的成员变量threadLocals
      t.threadLocals = new ThreadLocalMap(this, firstValue);
}

public class ThreadLocalTest {

    static ThreadLocal threadLocal = new ThreadLocal();

    public static void main(String[] args) {
        //在main线程中添加main线程的本地变量
        threadLocal.set("mainVal");
        //新创建一个子线程
        Thread thread = new Thread(new Runnable() {
            @Override
            public void run() {
                System.out.println("子线程中的本地变量值:"+threadLocal.get());
            }
        });
        thread.start();
        //输出main线程中的本地变量值
        System.out.println("mainx线程中的本地变量值:"+threadLocal.get());
    }
}