How does G1 garbage collector behave in multithreaded code?

The G1 (Garbage-First) garbage collector is designed to handle the needs of applications that require concurrent garbage collection, particularly in multithreaded environments. It operates by breaking the heap into smaller regions, which allows for more efficient memory management, especially in applications with large heaps. The G1 collector prioritizes areas of the heap that are most likely to have unreachable objects, thus optimizing memory reclamation.

In multithreaded code, G1 operates multiple threads during garbage collection phases, which improves application performance and responsiveness. G1 divides the garbage collection process into distinct phases, including marking, evacuation, and cleanup, all of which can be executed concurrently, thus minimizing pause times and allowing applications to perform other tasks while memory is being managed. This behavior is particularly essential for applications with significant and concurrent memory usage.