The short answer is: No, as of version 2.5.1. If you’re building web applications with GWT and try to use Java 7 constructs, be careful. A few days ago I was bitten by a nasty surprise when I tried to write use Strings in a switch statement, for demonstration purposes please see the code below that I have adapted from the Hello World example of GWT in Action:
The code above compiles perfectly fine with the latest version of GWT, Eclipse and Java 7, but if you try to run in using the Development Mode, instead of the expected output in your web browser window, you will get run-time error in Eclipse:
21:17:33.280 [ERROR] [com.manning.gwtia.ch02.HelloWorld] Line 16: Cannot switch on a value of type String. Only convertible int values or enum constants are permitted
as an indication that you are still in Java 6 world when it comes to the language constructs you can use in GWT.
The situation is not hopeless, at least for people who can wait because it seems like support for Java 7 will soon appear in GWT, though I could not find the exact date when it will be. The following links include more information about recent GWT developments: