记录构造方法ThreadLocal赋值失败---

省流：构造方法在主线程里跑的

先贴代码

public class Test {

    @SneakyThrows
    public static void main(String[] args) {
        ExecutorService execute = Executors.newSingleThreadExecutor();
        execute.execute(new T1("once"));
        execute.execute(new T1(null));
        Thread.sleep(1000);
        execute.shutdownNow();
    }

    static class T1 implements Runnable {
        static final ThreadLocal<String> str = new ThreadLocal<>();

        @SneakyThrows
        public T1(String a) {
            if (a != null){
                str.set(a);
                System.out.println("set str");
            }
        }
        @Override
        public void run() {
            System.out.println(Thread.currentThread().getId());
            System.out.println(str.get());
        }
    }

}

期望输出：

set str
线程id
once
线程id
null

实际输出：

 

 问题分析步骤：

debug分析 摇人最快

@SneakyThrows
        public T1(String a) {
            if (a != null){
                System.out.println(Thread.currentThread().getId());
                str.set(a);
                System.out.println("set str");
            }
        }

在这打印下线程号，执行一下问题就知道了