Java HashMap Race Condition: Multi-thread inserts cause OOM or infinite loop

In a heavily concurrent application using HashMap, the program sometimes crashes with OutOfMemoryError, or iteration behaves incorrectly. What’s causing it, and how do I fix it?

HashMap is not thread-safe. Concurrent writes to the same map can corrupt its internal structure—leading to infinite loops during iteration or excessive resizing, potentially causing JVM crashes ([turn0search8][turn0search0]). Fix: • Use ConcurrentHashMap for thread-safe access. • Or wrap access in synchronized blocks when mutating. • For lazy initialization of shared caches, combine volatile, double-checked locking, and computeIfAbsent() to ensure safe thread-safe behavior.