http://download.java.net/jdk6/docs/api/javax/lang/model/SourceVersion.html#isKeyword(java.lang.CharSequence)

says

"Returns whether or not s is a keyword or literal in the latest source version."

This method seems unreliable because it could change from release to release. E.g. in 1.3 this would return false for "assert" but true in 1.4+.