Java Articles

Track Native Memory Usage in Java with NMT

Java Native Memory Tracking NMT is a powerful debugging tool that lets you see exactly where your JVM is allocating memory outside the Java heap.

3 min read

Manage Off-Heap Memory in Java with DirectByteBuffer

Java's garbage collector is famously hands-off when it comes to memory management, but that doesn't mean it controls all memory.

2 min read

Instrument Java Services with OpenTelemetry Tracing

Java services can trace their requests across distributed systems using OpenTelemetry, but it's not just about adding a JAR; it's about understanding ho.

3 min read

Profile Java CPU and Memory with JFR and Async Profiler

Java's garbage collector isn't a mysterious black box; it's a highly configurable system that you can tune to perform better for your specific applicati.

3 min read

Build Reactive Java Applications with Project Reactor

Project Reactor lets you build reactive Java applications, but the real magic isn't just asynchronous programming; it's about declaratively managing str.

4 min read

Use Java Records, Sealed Classes, and Pattern Matching Together

Java Records, Sealed Classes, and Pattern Matching, when combined, offer a powerful, declarative, and type-safe way to model and process data.

2 min read

Java Reflection vs MethodHandles: Performance and Security Tradeoffs

Java Reflection is a powerful tool, but it’s also a performance and security minefield. Let's see MethodHandles in action

3 min read

Java REST Clients: HttpClient vs Feign vs RestTemplate Compared

Java's REST clients are a minefield, and the standard HttpClient is often the least surprising, but Feign and RestTemplate have their own, often hidden,.

3 min read

Debug Java Safepoint Pauses That Cause Latency Spikes

Java's safepoint mechanism, designed to bring all threads to a consistent state for operations like garbage collection or deoptimization, is often the h.

4 min read

Secure Java Applications with the OWASP Java Security Checklist

Java applications often have security vulnerabilities that are surprisingly easy to exploit, even in well-established frameworks.

3 min read

Replace Java Serialization with Jackson, Kryo, or Protobuf

Replace Java Serialization with Jackson, Kryo, or Protobuf — practical guide covering java setup, configuration, and troubleshooting with real-world exa...

4 min read

Fix Java Stream API Performance Pitfalls in Hot Paths

The Java Stream API is failing because its lazy evaluation and intermediate operations are causing excessive object creation and garbage collection pres.

4 min read

How Java String Interning Works and When to Use String.intern()

Java's String interning is a performance optimization that can save you a surprising amount of memory by ensuring that only one copy of any given string.

3 min read

synchronized vs ReentrantLock vs StampedLock in Java

Java's synchronized keyword, ReentrantLock, and StampedLock all aim to provide thread-safe access to shared resources, but they do so with different phi.

5 min read

Write Advanced Mockito Tests: Captures, Answers, and Spies

Mockito's capture and answer features let you introspect and manipulate behavior during tests, going beyond simple argument matching.

4 min read

Configure Java ThreadPoolExecutor for High-Throughput Applications

The ThreadPoolExecutor in Java is not just a pool of threads; it's a sophisticated, stateful machine that orchestrates task execution, and its configura.

4 min read

Use Java Virtual Threads (Project Loom) for Scalable Concurrency

Java's virtual threads, born from Project Loom, let you write concurrent code as if you were writing sequential code, but with the scalability of lightw.

4 min read

Java volatile vs AtomicInteger vs synchronized: When to Use Each

Java's volatile keyword, AtomicInteger, and synchronized blocks all deal with concurrent access to shared variables, but they operate at fundamentally d.

4 min read

Deploy Java Applications with Zero Downtime

Java applications can be deployed with zero downtime by orchestrating multiple instances of the application and carefully managing traffic flow between .

2 min read

Fix Java "Package Does Not Exist" Compilation Errors

Fix Java "Package Does Not Exist" Compilation Errors — The javac compiler is failing because it can't find the .class files for classes you're trying to...

3 min read

Fix Java "Reached End of File While Parsing" Errors

This error means the Java compiler found the end of a source file unexpectedly, before it could finish understanding the code structure it was expecting.

3 min read

Fix Java "Types Are Not Compatible" try-with-resources Errors

The Java compiler is throwing a "Types are not compatible" error when you try to use a try-with-resources statement because the object you're trying to .

3 min read

Fix Java "Unsupported Class File Major Version" Errors

The Java Virtual Machine JVM is refusing to load a class file because its version number is too high for the installed Java runtime environment.

4 min read

Fix Java "Variable Might Not Have Been Initialized" Errors

This error means the compiler can't guarantee that a variable will have a value assigned to it before it's used, even though your code looks like it sho.

4 min read

Fix Java "Array Required But Found" Type Errors

This error means the Java compiler expected an array of a certain type but found something else, usually a single object or null.

5 min read

Fix Java NoClassDefFoundError: Class Missing at Runtime

The Java Virtual Machine JVM gave up on loading a class that was present at compile time because it couldn't find the definition of that class at runtim.

3 min read

Fix Java "Class is Public, Should Be Declared in Its Own File"

The Java compiler javac is refusing to compile your code because it found a public class that isn't in a file with a matching name, which is a fundament.

4 min read

Fix Java "Duplicate Class" Compilation Errors

The Java compiler is throwing a "Duplicate Class" error because it's encountering two or more class definitions with the exact same fully qualified name.

4 min read

Fix Java "Incompatible Types: Found, Required" Errors

This error means the Java compiler found an object of one type when it was expecting an object of a different, incompatible type.

5 min read

Migrate Java Code to Java 21: Records, Sealed Classes, and Virtual Threads

Records and sealed classes are syntactic sugar that make certain common Java patterns more concise and robust, while virtual threads are a fundamental s.

4 min read

Build Compile-Time Code Generators with Java Annotation Processing

Annotation processing in Java is a compile-time mechanism that allows you to generate new source code based on annotations present in your existing code.

2 min read

Builder vs Factory vs Abstract Factory: When to Use Each in Java

The most surprising truth about design patterns like Builder, Factory Method, and Abstract Factory is that they aren't about creating objects, but about.

4 min read

Manipulate Java Bytecode at Runtime with ASM and ByteBuddy

Manipulate Java Bytecode at Runtime with ASM and ByteBuddy — practical guide covering java setup, configuration, and troubleshooting with real-world exa...

4 min read

Implement Circuit Breakers in Java with Resilience4j

Java's circuit breaker implementations, particularly with Resilience4j, are less about "preventing failures" and more about "gracefully degrading servic.

3 min read

Isolate Dependencies with Java ClassLoader Hierarchy

The Java ClassLoader hierarchy is designed to load classes into the JVM, but its inherent delegation model can paradoxically make it difficult to isolat.

3 min read

HashMap vs TreeMap vs LinkedHashMap: Java Collections Under the Hood

The surprising truth about Java's Map implementations is that HashMap doesn't actually store your keys in insertion order, or any predictable order for .

3 min read

Master Async Programming in Java with CompletableFuture

Java's CompletableFuture doesn't just make asynchronous programming easier; it fundamentally shifts how you think about concurrent operations from a "fi.

3 min read

Tune HikariCP Connection Pool Settings for Production

HikariCP's default settings are so aggressive that they can actually hurt performance under load by causing unnecessary connection churn.

4 min read

CDI vs Spring DI: Choose the Right Dependency Injection in Java

CDI and Spring DI are both powerful dependency injection frameworks in Java, but they approach the problem from fundamentally different philosophical st.

3 min read

Configure JVM for Docker: Container-Aware Heap and CPU Settings

The most surprising thing about configuring JVM heap and CPU for Docker is that the JVM often doesn't know it's in a container, leading to it hogging re.

4 min read

Profile Production Java Applications with JDK Flight Recorder

Flight Recorder is the most powerful, low-overhead profiling tool built into the JDK, yet most Java developers never even touch it.

3 min read

Write Functional-Style Java with Lambdas and Streams

Java's streams offer a surprisingly powerful way to write declarative, data-processing code that often feels more like SQL than traditional imperative J.

2 min read

G1 vs ZGC vs Shenandoah: Choose and Tune the Right Java GC

The most surprising true thing about Java garbage collection is that the choice of collector is less about raw speed and more about predictable latency,.

3 min read

Java Generics Type Erasure Explained with Practical Consequences

Java generics are a compile-time-only feature, meaning that at runtime, the JVM doesn't know about the type parameters you've specified.

3 min read

Build GraalVM Native Images for Instant Startup Java Apps

GraalVM native images can actually make your Java applications slower on initial startup if you're not careful, even though they promise instant cold st.

2 min read

Fix Hibernate N+1 Query Problems with Fetch Joins

Fix Hibernate N+1 Query Problems with Fetch Joins — The Hibernate QueryException: could not resolve collection: ... error means that a lazy-loaded colle.

3 min read

Senior Java Engineer Interview Questions and Answers

Senior Java Engineer Interview Questions and Answers — practical guide covering java setup, configuration, and troubleshooting with real-world examples.

3 min read

Master Jackson Serialization: Annotations, Modules, and Custom Serializers

Jackson's serialization isn't just about turning objects into JSON; it's about precise control over how that transformation happens, often in ways that .

3 min read

How Java JIT Tiered Compilation Speeds Up Your Application

The Java Virtual Machine JVM doesn't just run your Java code; it actively rewrites it on the fly to make it faster, and the secret sauce is "tiered comp.

3 min read

How the JVM Loads Classes: Bootstrap, Extension, and Application ClassLoaders

The JVM doesn't just have classes; it has a sophisticated, layered system for finding and loading them, and the most surprising thing is that your code .

3 min read

Tune JVM Heap Size and GC Flags for Production Performance

Tuning JVM heap size and GC flags for production performance isn't about making your application faster, it's about making it predictable.

6 min read

Build Production Kafka Consumers and Producers in Java

Kafka's brilliance isn't in its durability, it's in its ability to make future systems predictable by making past systems immutable.

3 min read

Fix Java ArrayIndexOutOfBoundsException

The ArrayIndexOutOfBoundsException is occurring because a Java program is attempting to access an element in an array using an index that is either nega.

5 min read

Fix Java NoClassDefFoundError in Production and Tests

Fix Java NoClassDefFoundError in Production and Tests — The java.lang.NoClassDefFoundError happens when the Java Virtual Machine JVM loads a class at ru...

4 min read

Fix Java NoSuchMethodError Caused by Classpath Conflicts

The NoSuchMethodError you're seeing means a Java application tried to call a method that it expected to find in a loaded class, but that method wasn't t.

5 min read

Fix Java StringIndexOutOfBoundsException

The StringIndexOutOfBoundsException means a Java program tried to access a character in a String using an index that doesn't exist.

4 min read

Fix Java UnsatisfiedLinkError for Missing Native Libraries

Fix Java UnsatisfiedLinkError for Missing Native Libraries — practical guide covering java setup, configuration, and troubleshooting with real-world exa...

3 min read

Lombok vs Java Records: Which Reduces Boilerplate Better?

Lombok vs Java Records: Which Reduces Boilerplate Better? — practical guide covering java setup, configuration, and troubleshooting with real-world exam...

2 min read

MapStruct vs ModelMapper: Performance and Type Safety Comparison

MapStruct and ModelMapper, both popular Java libraries for object-to-object mapping, tackle a common development task with surprisingly different philos.

2 min read

Detect and Fix Java Memory Leaks with Heap Dump Analysis

A Java memory leak isn't about Java using too much memory; it's about Java holding onto memory it no longer needs, preventing the garbage collector from.

6 min read

Java Memory Model Explained: Visibility, Ordering, and Happens-Before

The Java Memory Model JMM is designed to let you write multithreaded code without worrying about the specific CPU architecture or compiler optimizations.

5 min read

Quarkus vs Spring Boot: Choose the Right Java Microservice Framework

Quarkus and Spring Boot aren't just different Java frameworks; they represent fundamentally different philosophies about how to build and run microservi.

2 min read

Use the Java Module System (JPMS) in Real Applications

The Java Module System JPMS, introduced in Java 11, doesn't just organize code; it fundamentally redefines how Java applications are built, deployed, an.

3 min read

Manage Java Monorepos with Gradle Multi-Project Builds

Gradle's multi-project builds are the secret sauce for taming Java monorepos, allowing you to manage a single, massive codebase as a collection of small.

2 min read