Sun's implementation of JDK 6 is co-bundled with the Mozilla Rhino based JavaScript script engine. (...)
Rhino's JavaAdapter has been removed. JavaAdapter is the feature by which a Java class can be extended by JavaScript and Java interfaces may be implemented by JavaScript. This feature also requires a class generation library. We have replaced Rhino's JavaAdapter with Sun's implementation of the JavaAdapter. In Sun implementation, only a single Java interface may be implemented by a JavaScript object.
In other words, the Rhino distributed with JDK 6 provides no JavaAdapter functionality the Proxy class can't already achieve....