This code demonstrates a race condition when the object that is used as a lock is pointing to a new reference.

Main.java

// MyObject.java: https://gist.github.com/bjpeterdelacruz/b1a5b14f3d222fb30468b6edf4f3ce82
import java.util.stream.IntStream;

public class Main {
    public static void main(String[] args) {
        Runnable runnableA = MyObject::doSomething;
        Runnable runnableB = MyObject::reinitialize;

        for (var idx = 0; idx < 1000; idx++) {
            var threads = IntStream.range(0, 1000)
                    .mapToObj(i -> new Thread(i % 2 == 0 ? runnableA : runnableB))
                    .toList();

            threads.forEach(Thread::start);

            threads.forEach(t -> {
                try {
                    t.join();
                } catch (InterruptedException e) {
                    throw new RuntimeException(e);
                }
            });

            if (MyObject.getCounter() != 100000) {
                System.out.println("Race condition occurred. Counter value: " + MyObject.getCounter());
            }

            MyObject.resetCounter();
        }
    }
}