Talk:How to perform HTML entity encoding in Java
The Apache Jakarta Commons Lang package (as of version 2.2) contains a StringEscapeUtils class that contains this functionality. See the escapeHtml(String) method. The documentation states:
Escapes the characters in a String using HTML entities.
Supports all known HTML 4.0 entities, including funky accents. Note that the commonly used apostrophe escape character (') is not a legal entity and so is not supported).