Infosys Java Interview Questions 2026

Java memory is divided into Heap (objects) and Stack (method frames, primitives). Heap has: Young Generation (Eden + Survivor spaces) for new objects, Old Generation (Tenured) for long-lived objects. GC algorithms: G1GC (default Java 9+, good for large heaps), ZGC (low latency, Java 15+), Parallel GC (throughput focused). For tuning: monitor GC pause times with -verbose:gc, increase heap with -Xms/-Xmx, and use GCEasy.io for analysis.

ArrayList uses a dynamic array: O(1) random access by index, O(n) insertion/deletion in the middle. LinkedList uses doubly-linked nodes: O(1) insertion/deletion at known positions, O(n) random access. Use ArrayList for most cases (better cache locality, less memory). Use LinkedList only when you frequently insert/delete at both ends (implement Queue/Deque). In interviews, always ask about the access pattern before choosing.