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What is this?

This simple command line tool looks at Java class files and determine the format version number. The common use case of this tool is to figure out what is the offending jar file when you see UnsupportedClassVersionError.


This tool can accept any number of:

  • Class files
  • Jar files
  • Directories

When directories are given, they are recursively scanned for class files and jar files. When jar files are given, class files in it is examined.

The tool produces output like the following, so use the grep command to filter out the list:

% java -jar target/animal-sniffer-1.0-SNAPSHOT.jar tmp
50.0 tmp/streambuffer-0.7.jar:com/sun/xml/stream/buffer/AbstractCreator.class
50.0 tmp/streambuffer-0.7.jar:com/sun/xml/stream/buffer/AbstractCreatorProcessor.class
50.0 tmp/streambuffer-0.7.jar:com/sun/xml/stream/buffer/AbstractProcessor.class
50.0 tmp/streambuffer-0.7.jar:com/sun/xml/stream/buffer/AttributesHolder.class
50.0 tmp/streambuffer-0.7.jar:com/sun/xml/stream/buffer/FragmentedArray.class
50.0 tmp/streambuffer-0.7.jar:com/sun/xml/stream/buffer/MutableXMLStreamBuffer.class
50.0 tmp/streambuffer-0.7.jar:com/sun/xml/stream/buffer/XMLStreamBuffer.class
50.0 tmp/streambuffer-0.7.jar:com/sun/xml/stream/buffer/XMLStreamBufferException.class