Memory Leak in Java: Objects retained unexpectedly, OutOfMemoryError

My Java application gradually consumes more memory and eventually throws: makefile Copy code java.lang.OutOfMemoryError: Java heap space What commonly causes such memory leaks, and how do I detect and resolve them?

Despite Java’s garbage collection, memory leaks happen when objects remain referenced unnecessarily, preventing reclamation. Common causes: • Static collections or singletons holding onto objects indefinitely Wikipedia+15Programmer Sought+15Reddit+15RedditGeeksforGeeks • Unclosed resources like InputStream, JDBC Connection, etc.—leading to resource leaksSematext • Observer/listener patterns without deregistration (the “lapsed listener” problem)Wikipedia • ThreadLocal usage in thread pools without cleanup—values hang around beyond their intended scopeWikipedia+11Medium+11Sematext+11 🔍 How to Detect • Monitor heap growth via tools: VisualVM, Eclipse MAT, Java Mission Control, YourKitGeeksforGeeks+1Oracle Docs+1 • Profile using heap snapshots or memory leak analyzers 🛠️ How to Fix • Remove items from static collections or clear references when no longer needed • Use try-with-resources or finally blocks to close streams, connections, result sets Reddit+9Sematext+9GeeksforGeeks+9 • Properly deregister listeners from observer patterns • Explicitly call threadLocal.remove() when done