Blog
Production error deep-dives — root cause, reproduction, and the fix that holds.
Java Deadlock: Detect It, Read the Dump, Prevent It
Found one Java-level deadlock in a thread dump? How to read it, what ThreadMXBean misses (virtual threads, pool starvation), and the fixes that hold.
How to Read a Java Stack Trace, Line by Line, Fast
How to read a Java stack trace: what each line means, why the top frame can mislead you, and how to find the frame that actually matters in under a minute.
Java Exception With No Stack Trace: Why Traces Go Missing
A Java exception with no stack trace, or one cut off at 1024 frames, isn't a logging bug. Why the JVM drops traces, how to spot it, and what to change.
How to Use synchronized Blocks and Methods Correctly in Java
Learn how to use Java's synchronized keyword correctly — with real payment and banking examples covering race conditions, synchronized methods, blocks, deadlock-free transfers, double-checked locking, and virtual thread pitfalls. Covers Java 8 through 21
How to Use CompletableFuture for Async Programming in Java
Learn how to use Java's CompletableFuture for async programming — with real payment pipeline examples covering supplyAsync, thenCompose, thenCombine, error handling, and custom thread pools. Covers Java 8, 9, and 21.
ThreadPoolExecutor Explained: Pools, Queues, Rejection
Why your pool never grows past core size. How ThreadPoolExecutor admits tasks, why the queue fills first, and what each rejection policy does, with lab output.
Virtual Thread Stack Traces in Java, Decoded Line by Line
A virtual thread stack trace looks normal, minus the carrier. Why the thread name is empty, what each frame means, and how StructuredTaskScope rethrows.
NullPointerException in switch: null selector and case null
A switch on a null String, enum, Integer or sealed type throws NullPointerException, and default won't catch it. Why, how 8 to 25 differ, and the fix.
How to Use ScheduledExecutorService for Periodic Tasks in Java
Learn how to use Java's ScheduledExecutorService for periodic tasks — with real Kafka and payment pipeline examples covering scheduleAtFixedRate, scheduleWithFixedDelay, exception handling, graceful shutdown, and virtual threads. Covers Java 8 through 21.
InvocationTargetException with a null message: finding the real cause
Method.invoke wraps everything its target throws in an InvocationTargetException with no message. Here's how to see the real cause, on JDK 8 through 25.