In Java, the heap space is divided into two main regions: the young generation and the old generation.
The young generation is where new objects are created. It is divided into two parts: the Eden space and the survivor space. When an object is created, it is first allocated in the Eden space. If the Eden space becomes full, some of the objects that are still in use are moved to the survivor space. The survivor space is further divided into two regions: S0 and S1. The garbage collector (GC) moves live objects from one survivor space to the other, while also collecting any dead objects.
The old generation is where objects that have survived several garbage collections are moved to. These objects are typically long-lived and will persist for the duration of the application.
The garbage collector in Java is responsible for cleaning up unused objects. It works by periodically running in the background and identifying objects that are no longer being used by the application. The garbage collector frees up the memory used by these objects so that it can be used by other objects that are still in use.
The garbage collector uses several algorithms to determine which objects are no longer being used, such as reference counting, mark-and-sweep, and generational collection. These algorithms work together to ensure that all unused objects are removed from memory in a timely and efficient manner.
In general, it is not recommended to use the System.gc() command in production code. This is because the garbage collector is already designed to run automatically and efficiently in the background, and forcing it to run may have a negative impact on performance. Additionally, calling System.gc() can lead to unpredictable behavior, such as unexpected pauses in the application, which can be problematic in production environments. Instead, it is best to rely on the automatic garbage collection provided by the JVM.