What's the difference between Synchronized and Lock in my example?

Question

I wrote a simple code to mock concurrency using Lock and synchronized.

Source code is as follows:

Task class inclu

Answer 1

synchronized ("A")

it's not a proper usage of synchronized block. you create a different String object (in some cases) when entering this sync block, so each your thread have a different lock object and do not synchronize. Proper usage may be like

synchronized(this)

or

public class TaskWithSync extends Task implements Runnable {
    private Object lock = new Object();

    @Override
    public void run() {

        synchronized (lock) {
            doSomething();
        }
    }
}

In addition, you should use a single Runnable implemenation in different threads, or make your lock a static field