To assist Java programming educations, we have developed a Web-based Java Programming Learning Assistant System (JPLAS). JPLAS provides fill-in-blank problems to study the Java grammar by filling blank elements in a high-quality code that are composed of reserved words, identifiers, and control symbols. A graph-based blank element selection algorithm has been proposed to automatically select as many blanks as possible that have grammatically correct unique answers. In this paper, we show and discuss their application results to a Java programming course in our department.