关于Java中的同步方法

Question

I have a question about synchronization of methods in Java.

Consider a class with 3 synchronized methods.

class MyClass{

    public synchronized void methodA(){ ... }

    public synchronized void methodB(){ ... }

    public synchronized void methodC(){ ... }

}

Consider myObject , an instance of myClass . Which of the following is true?

Option 1:

It's impossible for a thread to run any synchronized method in myObject , while a different thread is running any synchronized method in myObject .

For example, while thread 1 is running methodA() of the instance myObject , thread 2 can't run any of the methods methodA() , methodB() and methodC() .

Option 2:

It's impossible for a thread to run a specific synchronized method in myObject , while that specific method is being run by another thread.

For example, while thread 1 is running methodA() of the instance myObject , thread 2 can't run the method methodA() , but can run methodB() or methodC() . (Meaning, the three synchronized methods aren't 'connected').

Answer 1

第一个选项是正确的，因为基本上有一个锁用于所有方法。