小编use*_*415的帖子

// the java source code
public class Demo {
    private final Object lock = new Object();

    public void read() {
        synchronized (lock) {
            // more code here ...
        }
    }
}

// the decompiled .class file
public class Demo {
    private final Object lock = new Object();

    public void read() {
    // Why Java compiler add this line? Is the 'read this.lock' redundant?
    Object var1 = this.lock;
    synchronized(this.lock) {
        // more code here ...
    }
    }
}

字节码在这里：javap …