How does Garbage Collector work in general terms?

Garbage Collector (GC) in Java automatically manages memory by freeing objects that are no longer in use by the program. In general, GC works as follows:

1. Reachability Tracking of Objects: GC determines which objects are reachable from root references (stack, static variables, etc.). Objects that are not reachable from roots are considered garbage.

2. Memory Division into Generations: Usually, the heap is divided into the Young Generation and the Old Generation. The Young Generation is collected more frequently because most objects quickly become unnecessary.

3. Garbage Collection:

   • In the Young Generation, a copying algorithm is used, where live objects are copied to another memory area.
   • In the Old Generation, marking and sweeping or marking and compacting algorithms are used.

4. Application Pauses: During garbage collection, the application may be paused (Stop-the-World), which affects performance.

Example of a simplified GC cycle:

// Objects are created
Object obj = new Object();
// If obj is no longer used and there are no references to it, GC will free the memory

Modern JVMs use different GC implementations (G1, ZGC, Shenandoah), optimized to minimize pauses and efficiently utilize memory.