http://java.sun.com/j2se/JM_White_Paper_R6A.pdf
This guide helps developers migrate Java applets, standalone applications, Java Web Start applications, and development tools from version 1.3 of the Java platform to version 5.0.
While many 1.3 applications run without change, compatibility issues do exist, as described in this guide. The first three sections cover issues that are of interest to all application developers. The fourth section covers issues that are primarily of interest to platform implementers and tool developers.
