For example, in the following test code, Eclipse will offer to "exchange left and right operands for infix expression" when you try a quick fix (cmd-1 on a Mac, ctrl-1 elsewhere) at the '&&' on line 2. The refactoring transforms "(a || b) && c" into "c && a || b".
boolean a = true, b = true, c = false;
boolean original = (a || b) && c;
boolean swapped = c && a || b;
assertTrue(!original); // ok
assertEquals(original, swapped); // fail
Note that the parentheses have disappeared - at first I assumed that they must therefore be unnecessary and "c && a || b" is therefore equivalent to "c && (a || b)", but figured that the parser should evaluate from left to right (which would produce different results). Being unconvinced one way or the other, I made a simple testcase to verify that both expressions were logically equivalent, which failed.
I'm not sure why Eclipse removed the parentheses, and it doesn't really matter - the point is, keep an eye on what your code transformation utility is doing - don't assume that it must produce correct output. This was one of those cases where the logic bug might not show up for a while, and the existing unit tests wouldn't have caught it, unless I bothered to run a (probably outdated and slow) integration test.