Foo instance = new Foo();

public class Bar {
    protected static final ReentrantLock lock = new ReentrantLock();

    public void process() {
        Foo instance = new Foo();
        boolean locked = false;
        try{
            if(SomeCondition) {
                locked = true;
                Bar.lock.lock();
            }

            *//rest of the processing goes here

        } finally {
            if(locked){
                Bar.lock.unlock();
            }
        }
    }
}