Java同步锁定类，而不是对象？

最近我读了Bruce Eckel（用Java思考），发现了一些问题：块同步（对象）锁定类！不是这个类的对象。本规范证明了上述内容：

public class Main {

    public static void main(String[] args) {
        Sync s = new Sync();
        new Thread(new Runnable() {
            @Override
            public void run() {
                s.go();
            }
        }, "First").start();
        new Thread(new Runnable() {
            @Override
            public void run() {
                s.go();
            }
        }, "Second").start();
    }
}

class Sync {

    private Writer w1, w2;

    public Sync() {
        w1 = new Writer();
        w2 = new Writer();
    }

    public void go() {
        synchronized (w2) {
            w1.log(Thread.currentThread().getName() + "...1");
            //!All threads must performance parallel, but they do it consistently.
            w2.log(Thread.currentThread().getName() + "...2");
            //All threads must performance parallel, and they do it.
        }
    }
}

class Writer {
    public void log(Object obj) {
        for (int i = 0; i < 5; i++) {
            lgn(obj);
            try {
                TimeUnit.MILLISECONDS.sleep(750);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }
}

预期产量

First...1
Second...1
First...1
Second...1
First...1
Second...1
First...1
Second...1
First...1
Second...1
First...2
First...2
First...2
First...2
First...2
Second...2
Second...2
Second...2
Second...2
Second...2

p.S对不起我的英语（

synchronized（w2）

表示我们使用w2创建锁，而不是锁定对象w2。您可以使用任何其他对象创建锁，并且同步块中的代码仍然被锁定

class Sync {

    private Writer w1, w2;
    private Object whatEver;

    public Sync() {
        w1 = new Writer();
        w2 = new Writer();
        whatEver = new Object();
    }

    public void go() {
        synchronized (whatEver) {
            w1.log(Thread.currentThread().getName() + "...1");
            //!All threads must performance parallel, but they do it consistently.
            w2.log(Thread.currentThread().getName() + "...2");
            //All threads must performance parallel, and they do it.
        }
    }
}

---

请用英语回答。我投票将这个问题作为离题题结束，因为它属于我翻译过的）看起来你锁定了Writer w2

synchronized（w2）

并没有阻止另一个线程与

w2

：它阻止另一个线程进入相同的

synchronized（w2）

块。（注意：它还会阻止其他线程进入任何其他

synchronized（w2）

块，但在您的示例中，您只有一个这样的块。）

class Sync {

    private Writer w1, w2;
    private Object whatEver;

    public Sync() {
        w1 = new Writer();
        w2 = new Writer();
        whatEver = new Object();
    }

    public void go() {
        synchronized (whatEver) {
            w1.log(Thread.currentThread().getName() + "...1");
            //!All threads must performance parallel, but they do it consistently.
            w2.log(Thread.currentThread().getName() + "...2");
            //All threads must performance parallel, and they do it.
        }
    }
}