How about a refactoring that will create a decorated class based on an existing supplied interface/class :
Id like to make a decorated Statement :
public class MyStatement implements Statement
private Statement statement;
public ResultSet executeQuery()
This could easily be automated - as it is now, its a pain in the neck, especially when IDEA can already create all the interface methods, but it creates them with "default" return values - it woiuld be nice if the "implement interface" refactoring could be told to delegate all calls to the data member.