When you use code completion in Java, you can finish selection from the suggestion list with an exclamation mark. So doing, the exclamation mark will be placed before a Boolean method or variable being completed, thus negating the whole expression.
- Start typing an expression, and press ⌃Space or ⌃Space⌃Space or ⌃Space⌃Space or ⌃Space^ Space, ⌃Space or ⌃Space⌥ Slash, ⌥/ or ⌥/.
- In the suggestion list, select the desired part of the expression.

- Press ! key. Your expression is completed with negation:
