What happens when a singleton object is pointing to a new reference?

MyObject.java

public final class MyObject {
    private static int counter = 0;
    private static Object lock = new Object();

    public static void doSomething() {
        synchronized (lock) {
            for (int i = 0; i < 100; i++) {
                counter++;
            }
        }
    }

    public static void reinitialize() {
        synchronized (lock) {
            try {
                Thread.sleep(5);
            } catch (InterruptedException e) {
                throw new RuntimeException(e);
            }
            lock = new Object();
        }
    }

    public static int getCounter() {
        return counter;
    }

    public static void resetCounter() {
        counter = 0;
    }
}