The article examines the role of the volatile modCount field in Java’s HashMap fail‑fast iterator, shows how its declaration changed from JDK5/6 to JDK7/8, and explains why ConcurrentModificationException can occur even in single‑threaded contexts.
This article explains why modifying a collection during a Java foreach loop triggers a ConcurrentModificationException, explores the underlying fail‑fast mechanism in ArrayList, and demonstrates safe alternatives such as using an Iterator's remove method or a CopyOnWriteArrayList.
The article clarifies that the modCount field in java.util.HashMap is used to implement the fail‑fast iterator behavior, explains why the field was volatile in early JDK versions but not in later ones, and shows that ConcurrentModificationException can be thrown even in single‑threaded scenarios when the iterator detects structural changes.
This article explains the common JVM OutOfMemoryError categories, analyzes a real‑world GC overhead limit exceeded incident, and demonstrates how applying the fail‑fast principle can help developers detect and resolve memory‑related failures more efficiently.
Facing rapid business growth, Dazhong Dianping’s payment gateway evolved through usable, flexible, and highly available stages, employing service splitting, master‑slave databases, fail‑fast mechanisms, and comprehensive monitoring to achieve 99.99% availability and handle peak traffic during major sales events.
