Why Does \'java.lang.UnsupportedClassVersionError: Bad version number\' Occur Even with Only One Java Version Installed?

java.lang.UnsupportedClassVersionError: Troubleshooting Bad Version Number in .class File

The "java.lang.UnsupportedClassVersionError: Bad version number in .class file" exception typically occurs when code compiled in a newer Java version is executed in an older version. However, in this case, the user has verified that only one Java version (1.5.0_18) is installed. What could be causing this error?

According to the responses, internal issues within a class can indeed cause this exception. The most likely culprit is that one of the user's Eclipse projects is compiling Java 1.6 classes, even though the system only has a Java 1.5 JRE.

Eclipse uses its own compiler, which can compile higher Java versions even with a lower JRE installed. The user needs to check the Project Properties for the affected project and ensure that the Java Compiler section is set to compile Java 1.5 classes. This can be done by unchecking the "Enable project specific settings" checkbox and selecting "Use default compiler settings."

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