Explain the working principle of the garbage collector (using G1 GC as an example)

G1 GC (Garbage-First Garbage Collector) is a modern garbage collector in JVM, focused on minimizing pauses and efficiently handling large heaps.

Main principles of G1 GC:

• Heap partitioning into regions: the heap is divided into many small regions of fixed size (usually from 1 to 32 MB).
• Tracking live objects: G1 maintains information about which regions contain the most garbage.
• Garbage collection in regions with the most garbage (Garbage-First): regions with the highest amount of unused objects are collected first, increasing efficiency.
• Young and old generations: regions are dynamically allocated between young and old generations.
• Incremental and parallel operation: G1 performs collection in parallel with application work, aiming to keep pauses within a specified time.

The process roughly looks like this:

1. G1 analyzes regions and selects those with the most garbage.
2. Parallel to application work, live objects are copied from selected regions to new regions.
3. Old regions are freed.
4. Full collections are periodically performed to clean fragmented regions.

This allows G1 to manage memory efficiently, reducing pauses and improving application predictability.