Java Syntactic Sugar

It is an initializer block, but not necessarily a static initializer block. It is effectively a constructor for an anonymous inner class. You will typically see this "double-brace initialization" pattern to conveniently create and populate collections:

private final Collection<Integer> FIXED_COLLECTION = Collections.unmodifiableCollection(new HashSet<Integer>() 
{ // first set of braces declares anonymous inner class
    { add(1); add(2); add(3); } // second set is initializer block
});

It's an instance initializer that calls the code within the context of the created object.

This is equivalent to

Expectations exp = new Expectations();
exp.oneOf(alarm).getAttackAlarm(null);
conext.checking(exp)

Whoever wrote it might have thought he was being more efficient by not declaring a variable (not true) or that it was cleaner code (I disagree).

The primary place that these initializers are useful like this is when instantiating maps, ie:

Map map = new HashMap() {{
  put("key1", "value1");   
  put("key2", "value2"); 
}};

which I think actually is slightly more readable.