我所知道的有两个已经开发好的API可以使用
一个是MIT大学开发的，叫JWI（the MIT Java WordNet Interface）.
JWI (the MIT Java Wordnet Interface) is a Java library for interfacing with Wordnet. JWI supports access to Wordnet versions 1.6 through 3.0. Wordnet is a freely and publicly available semantic dictionary of English, developed under the direction of George Miller at Princeton University.
JWI is written for Java 1.5.0 and has the package namespace edu.mit.jwi. The distribution does not include the Wordnet dictionary files; these can be downloaded from the Wordnetdownload site. This version of software is distributed under a license that makes it free to use for non-commerical purposes, as long as proper copyright acknowledgement is made. If you are interested in obtaining a commercial license, please contact the MIT Technology Licensing Office.
The javadoc API is posted online for your convenience. So is the version changelog. If you find JWI useful, have found a bug, or would like to request a new feature, please contactme.
http://projects.csail.mit.edu/jwi/还有一个是JWNL - Java WordNet Library