Suspend everything you know about Java (and programming in general) for a moment, and let's make some observations about our world. These may sound like obvious statements, but as developers, we can easily overlook them. Try to become aware of the fact that everything is in motion. Traffic, weather, people, conversations, financial transactions, and so on are constantly changing or moving through stages.
Technically, even something as stationary as a rock is in motion, as its spatial location changes constantly due to the earth's rotation and orbiting through space. When you consider the possibility that everything can be modeled as being in motion, you may find it a bit overwhelming as a developer.
Another observation to note is that these different events are happening concurrently. Multiple activities are happening at the same time. Sometimes,...