Types of GCs and Their Differences

Java's Garbage Collection (GC) is a memory management technique that automatically cleans up objects in the heap that are no longer in use. There are various GC algorithms, each optimized for different situations and requirements.

Serial GC #

This GC is very simple and runs on a single thread, making it best suited for systems where application response time is not critical. It is primarily used in environments with small heaps and limited CPU resources.

Parallel GC #

This GC is designed to optimize throughput. It stops all application threads during garbage collection (stop the world) and uses multiple GC threads concurrently to minimize GC processing time. This is suitable for server environments with many CPU cores.

Concurrent Mark Sweep (CMS) GC #

This GC is designed to optimize application response time. CMS GC performs most garbage collection tasks concurrently while application threads are running. However, this GC consumes significant CPU resources and can lead to memory fragmentation issues.

G1 (Garbage First) GC #

This GC offers a new approach by dividing the heap into multiple regions of the same size and managing each region independently. It improves efficiency by prioritizing collection from regions with the most garbage. This GC works well in systems with large heaps, and its goal is to reduce application pause times during garbage collection.

The performance of each GC can vary depending on the specific environment and requirements, so you should choose the appropriate GC based on your application's performance requirements and execution environment.