Diagnose and Troubleshoot

Quick Index

Troubleshooting Table
UnsupportedClassVersionError
Diagnostic Tools Cheat Sheet
Windows-Only Diagnostic Tools

Problem	Remedy
When compiling, this error is shown: "javac is not recognized"	See VerifyPath...
When you run the "java" command you get "UnsupportedClassVersionError ... has been compiled by a more recent version ..."	See UnsupportedClassVersionError

UnsupportedClassVersionError

Problem

When running your java program e.g. when running the

 "java Foo"

command, if you are getting errors something like these:

UnsupportedClassVersionError
has been compiled by a more recent version of the Java Runtime
(this file version 57.0), this version of the Java Runtime only recognizes
class file version up to 54.0

Fixing

This indicates that we are using a different version of "java.exe" (run) vs "javac.exe" (compile).

Because both "java.exe" and "javac.exe" are in the same directory ("...\java\bin"), this usually can be resolved by fixing the system path. See verify path.

Then check and ensure that the "%JAVA_HOME%\bin" line is at the top of the path variable as described here....

Diagnostic Tools Cheat Sheet

Command	Example	Notes
javac -version	>javac -version javac 11.0.2	The configured jdk version
java -version	>java -version java version '11.0.2' 2019-01-15 LTS	The version here should match that with the "javac -version" output
echo %JAVA_HOME%	>echo %JAVA_HOME% C:\Program Files\Java\jdk-11.0.2	Full path to your installed jdk
echo %path%	>echo %path% C:\Program Files\Java\jdk-11.0.2\bin; etc...	The output should start out with the full path to your jdk plus '\bin'

NOTES

Run the commands in the console
Some of these commands will need to be tweaked for MAC/Unix. For example, "echo %path%" would be "echo $PATH" for MAC/Unix.
The "java -verbose" can also be used to provide extra info

Windows-Only Diagnostic Tools

Command	Example	Notes
wmic os get osarchitecture	>wmic os get osarchitecture OSArchitecture 64-bit	64-bit indicates system is 64-bit, otherwise system is 32-bit
echo %PROCESSOR_ARCHITECTURE%	>echo %PROCESSOR_ARCHITECTURE% AMD64	'64' indicates system is 64-bit, otherwise system is 32-bit

Introduction To Objects With Java (Chapter 103 - Installing Java.xdoc)

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