Other
Horstmann: Java Language Coding Guidelines
A coding style guide for the Java programming language that has been used successfully in education and industry alike.
Other
Geotechnical Software Services : Java Programming Style Guidelines
This site describes Java coding recommendations that are common in the Java development community.
Other
Java Ranch: Java Programming Style Guide
An alternative style guide for writing clear code in the Java programming language.
Wikimedia
Wikipedia: Programming Style
A Wikipedia description of what constitutes good programming style.