public class OneThreadDemo {    public static void main(String[] args) throws InterruptedException {        ThreadLocal
    
      mainLocal = new ThreadLocal
     
      ();        mainLocal.set(1);        System.out.println(Thread.currentThread().getName() + mainLocal.get());        DemoThread t2 = new DemoThread(mainLocal, 2);        DemoThread t3 = new DemoThread(mainLocal, 3);        DemoThread t4 = new DemoThread(mainLocal, 4);        t2.start();        t3.start();        t4.start();        Thread.sleep(1000);        System.out.println(Thread.currentThread().getName() + mainLocal.get());    }}class DemoThread extends Thread {    private ThreadLocal
      
        mainLocal;    private Integer value;    public DemoThread(ThreadLocal
       
         local, Integer value) {        this.mainLocal = local;        this.value = value;    }    @Override    public void run() {        mainLocal.set(value);        Integer a = mainLocal.get();        System.out.println(Thread.currentThread().getName() + a);    }}
       
      
     
    

在一个线程定义了变量，传递给其他线程使用，对变量做更改，其他线程对所做的更改可见，但是定义ThreadLoacl那个线程不可线。俗称的线程本地化。