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⌃Space⌃Space^ Space⌥ Slash.
- In the suggestion list, select the desired part of the expression.
- Press ! key. Your expression is completed with negation:
