结论：同一个 ThreadLocal 变量不能在子线程中获取到，而 InheritableThreadLocal 变量中的值可以在父子线程之间传递。
例子：
public class Main {
private static ThreadLocal<String> threadLocal = new ThreadLocal<>();
private static InheritableThreadLocal<String> inheritableThreadLocal = new InheritableThreadLocal<>();
public static void main(String[] args) {
threadLocal.set("mainThread");
inheritableThreadLocal.set("hello");
Thread thread = new Thread(new Runnable() {
@Override
public void run() {
System.out.println("threadLocal: " + threadLocal.get()); // null
System.out.println("inheritableThreadLocal: " + inheritableThreadLocal.get()); // hello
}
});
thread.start();
}
}
输出：
threadLocal: null
inheritableThreadLocal: hello