In .NET i cannot imagine working without mocking frameworks like NSubstitute. But
every once in a while i do some Java. This autumn vacation i had a look at some mocking frameworks for Java. Starting with Stack Overflow: Comparison between Mockito vs JMockit - why is Mockito voted better than JMockit? i did some quick tests with JMockit. First impression: JMockit has all what you need and getting started is really easy.
After asking around i got responses that the arrange-syntax might be a little lighter in Mockito.
What mocking frameworks do you use?