Java while loop boolean evaluation

The while (!b) condition does not set b to true.

The b = !b statement does.

That's why your loop executes only once.

Translation in pseudo-code:

• while not b (that is, while b is false)
• print b (so print false)
• assign b to not b, that is, the opposite of b (so assign b to true)
• next iteration of the loop, b is true, so not b condition fails and loop terminates

Translated:

 boolean b = false;
 while(b == false) {
 System.out.println(b);
 b = !b;  // b becomes true
}

while(!b) {    // As b = false but due to ! condition becomes true not b
System.out.println(b);  //false will be printed
b = !b;  // b = !false i.e. now b is true 
}

As now b is true so in next iteration the condition will be false and you will exist from loop

! is the negation unary operator in Java a do not modify the operand.

boolean b = false;
while(!b) { // The !b basically means "continue loop while b is not equal to true"
System.out.println(b);
b = !b; // this line is setting variable b to true. This is why your loop only processes once.
}