Memory Management and Garbage Collection

Objects generally live on the heap; each invocation has a stack frame holding execution state and local values. The JVM may optimize placement while preserving observable behavior.

Reachability, not scope

List<byte[]> retained = new ArrayList<>();
// Retaining references keeps arrays reachable and prevents reclamation.
retained.add(new byte[1_000_000]);
retained.clear();

Collectors find objects unreachable from GC roots and reclaim them; timing is intentionally unspecified. Strong, soft, weak, and phantom references have different reachability roles. Java can still leak memory through caches, listeners, thread locals, and static collections. Heap sizing and collector choice are operational decisions driven by latency/throughput measurements. GC manages memory—not files, sockets, native handles, or business lifecycle—so close resources deterministically.