Java

Oracle JDK and OpenJDK use direct pointers: fast access, but pointers need to be updated if GC moves surviving objects.

Why OOM occurs and examples for heap, Metaspace, stack overflow, GC overhead, direct buffer memory, and native-thread exhaustion.

Built-in JDK tools such as jps, jinfo, jstack, jmap, jstat, and jhat, plus JMX, MAT, Java Mission Control, BTrace, flame graphs, YourKit, JProfiler, and GC log tools.

Which JVM parameters to tune, JVM parameter types, how to inspect them, common options, examples, and a typical configuration.

Parallel GC logs, tools, and references.

Whether creating a subclass object also creates a parent object, whether private fields are inherited, and references.

What reflection is, how it is used, how it works, and reference links.

Socket basics, TCP Socket/ServerSocket, UDP, and communication-protocol design.

Servlet lifecycle: init, service, destroy, garbage collection, and a reference.

JVM tuning, verifying JVM parameters, and Coyote Connector tuning.