ThreadLocal说明

public class Test {
 
    private ThreadLocal<String> stringThreadLocal = new ThreadLocal<>() ;
    private ThreadLocal<String> stringThreadLocal2 = new ThreadLocal<>() ;
 
    public void print() {
        System.out.println("threadName:" + Thread.currentThread().getName() + ",value:" + stringThreadLocal.get());
        System.out.println("threadName:" + Thread.currentThread().getName() + ",value:" + stringThreadLocal2.get());
    }
 
    public void setValue(String value) {
        stringThreadLocal.set(value);
        stringThreadLocal2.set(value + "——2");
    }
 
    public static void main(String[] args) throws InterruptedException {
 
        Test test = new Test() ;
        test.setValue("test0");
        test.print();
 
        Thread thread1 = new Thread(new Runnable() {
            @Override
            public void run() {
                test.setValue("test1");
                test.print();
            }
        }) ;
        thread1.start();
 
        Thread.sleep(1000);
 
        test.print();
    }
}

threadName:main,value:test0
threadName:main,value:test0——2
threadName:Thread-0,value:test1
threadName:Thread-0,value:test1——2
threadName:main,value:test0
threadName:main,value:test0——2

public T get() {
    //  获取当前线程
    Thread t = Thread.currentThread();
    // 获取当前Thread的map
    ThreadLocalMap map = getMap(t);
    if (map != null) {
        // 获取当前ThreadLocal对象对应的entry
        ThreadLocalMap.Entry e = map.getEntry(this);
        if (e != null) {
            @SuppressWarnings("unchecked")
            T result = (T)e.value;
            return result;
        }
    }
    return setInitialValue();
}
// 获取当前线程对应的map
ThreadLocalMap getMap(Thread t) {
    return t.threadLocals;
}
 
public void set(T value) {
    Thread t = Thread.currentThread();
    ThreadLocalMap map = getMap(t);
    if (map != null)
        map.set(this, value);
    else
        createMap(t, value);
}