Programming Tutorials

  You have just upgraded Flutter, Android Studio, or your JDK, and your build pipeline has halted with a stack trace resembling this: java.lang.IllegalArgumentException: Unsupported class file major version 61 Or perhaps version  65 . This is not a cryptic bytecode error; it is a rigid version mismatch. In the Java ecosystem, class file major versions correspond to specific JDK releases: 61  = Java 17 65  = Java 21 This error occurs when a build tool (specifically Gradle) running on an older JVM attempts to read classes compiled by a newer JDK, or when the Gradle version defined in your project is too old to support the JDK version you are forcing it to run on. With the release of Android Gradle Plugin (AGP) 8.0, the Android ecosystem has enforced a hard floor of  JDK 17 . If your Flutter project’s Gradle wrapper or AGP version is outdated, the build fails immediately. Here is the root cause analysis and the definitive, step-by-step upgrade path to resolve this ...

  The migration from Spring Boot 2.7 to Spring Boot 3.0+ is not a trivial version bump; it is a paradigm shift in the Java ecosystem. The most immediate and jarring obstacle developers face is the application crashing at startup with   java.lang.NoClassDefFoundError: javax/servlet/http/HttpServlet   or   java.lang.ClassNotFoundException: javax.persistence.Entity . This error signifies that your bytecode is referencing the legacy Java EE APIs ( javax.* ), but the runtime environment (Spring Boot 3 / Jakarta EE) only provides the modern Jakarta EE APIs ( jakarta.* ). The Root Cause: The "Big Bang" Namespace Shift To understand the fix, you must understand the architecture change. When Oracle transferred Java EE to the Eclipse Foundation to become Jakarta EE, they retained the trademark rights to the  javax  namespace. Consequently, starting with  Jakarta EE 9 , all specifications were legally required to move from the  javax.*  package namespac...