相当于Delphi的Java NOT

Question

In Delphi I can do the following with a boolean variable:

If NOT bValue then
begin
  //do some stuff
end;

Does the equivalent in Java use the !?

If !(bValue) {
  //do some stuff
}

Answer 1

You're close; the proper syntax is:

if (!bValue) {
  //do some stuff
}

The entire conditional expression must be inside the parenthesis; the condition in this case involve the unary logical complement operator ! ( JLS 15.15.6 ).

Additionally, Java also has the following logical binary operators:

• JLS 15.22.2 Boolean Logical Operators & , ^ and |
  • casually "and", "xor" and "or"
• JLS 15.23 Conditional-and && and JLS 15.24 Conditional-or ||
  • the much more frequently used short-circuiting "and" and "or"

There are also compound assignment operators ( JLS 15.26.2 ) &= , |= , ^= .

---

Other relevant questions on stackoverflow:

• Shortcut "or-assignment" (|=) operator in Java
• Why doesn't Java have compound assignment versions of the conditional-and and conditional-or operators? (&&=, ||=)
• What's the difference between | and || in Java?
• Cleanest way to toggle a Boolean variable in Java?
• Getting confused in with == and = in “if” statement
  • There are plenty of similar questions on stackoverflow due to accidental boolean assignment instead of comparison
  • You never need to write == true and == false
    • Omit explicit comparison with true and false
    • use ! when necessary

Answer 2

Yes, but inside the bracket:

if (!bValue) {
}

You'd normally not use any sort of data type prefix in Java as well, so it would more likely be something like:

if (!isGreen) { // or some other meaningful variable name
}

Answer 3

if (!bValue) {
    // do some stuff
}