In glosstag.properties must be set valid path to WordNet-3.0. Additionaly to initialize JWNL a file_properties.xml with proper content is needed. It contains path to WordNet-3.0 too. To compile exacute: javac -cp WordNetGlossTagLibrary.jar:. Example.java To execute type: java -cp WordNetGlossTagLibrary.jar:. Example