java.lang.UnsupportedClassVersionError: has been compiled by a more recent version of the Java Runtime — how to fix

Error: LinkageError occurred while loading main class com.example.App
        java.lang.UnsupportedClassVersionError: com/example/App has been compiled by a more recent version of the Java Runtime (class file version 65.0), this version of the Java Runtime only recognizes class file versions up to 55.0

Quick fix: Check java -version. Install/switch to the Java version that matches the class file version (65 = Java 21, 61 = Java 17, 55 = Java 11), or rebuild with --release 11 (Maven: <maven.compiler.release>11</maven.compiler.release>).

What it means

Every .class file records which Java version it targets. The JVM you're running is older than that and refuses to load it.

Class file version → Java version

In the example, the class needs Java 21 (65.0) but the runtime is Java 11 (55.0).

Fix 1: run it with a newer Java

java -version

Ubuntu/Debian: sudo apt install openjdk-21-jre and choose it with sudo update-alternatives --config java. macOS: brew install openjdk@21. SDKMAN works everywhere: sdk install java 21-tem.

Make sure JAVA_HOME and your IDE point to the same JDK. Multiple installed versions are the usual reason "but I installed Java 21!" still fails.

Fix 2: compile for the older Java

javac:

javac --release 11 App.java

Maven:

<properties>
  <maven.compiler.release>11</maven.compiler.release>
</properties>

Gradle:

java { toolchain { languageVersion = JavaLanguageVersion.of(11) } }

--release also stops you from using APIs that don't exist in the older version, unlike the old -source/-target flags.

It's a library, not your code

If the class belongs to a dependency (e.g. org/springframework/...), that library version requires a newer Java. Spring Boot 3 needs Java 17+, for example. Either upgrade Java or use an older library version.

In IntelliJ / Eclipse

Set the project SDK and the run configuration's JRE to the same version: IntelliJ File → Project Structure → Project SDK and Run → Edit Configurations → JRE.

Last updated 2026-10-27.