The changes look reasonable to me, although I don't think any of the changes are in particularly performance critical code. One little problem is that the changes in EmbedConnection40 and NetConnection40 remove code that's there to prevent a compiler warning (there must be an easier way to do it than how we do it now, though), so now the warning is back:
$ ant -q
[javac] Note: /code/derby/d5021/java/engine/org/apache/derby/impl/jdbc/EmbedConnection40.java uses unchecked or unsafe operations.
[javac] Note: Recompile with -Xlint:unchecked for details.
[javac] /code/derby/d5021/java/client/org/apache/derby/client/net/NetConnection40.java:349: warning: [unchecked] unchecked conversion
[javac] found : java.util.Map
[javac] required: java.util.Map<? extends java.lang.String,? extends java.lang.Class<?>>
[javac] Map<String, Class<?>> genericTypeMap = new HashMap<String, Class<?>>(typeMap);
[javac] 1 warning
Total time: 21 seconds