While 循环语句

Question

I am having trouble understanding some code in Java. I have researched around but I am still having trouble fully understanding it.

boolean showShip = false; //set the ship to be hidden by default

while(!showShip) //dont get this while loop
{
  val = promptForInt("\n" + "Guess again. "); 

  if(val == randomShipLocation)
  {
    System.out.println("\n" +" BOOM!");
    showShip = false;
    riverLength[val] = 1; // mark a hit
  }
  else {
    riverLength[val] = -1; // mark a miss
  }

  displayRiver(riverLength, showShip);
}

The part I am getting stuck on is the while(!showShip) part. What does this statement mean?

Answer 1

showShip is a boolean variable, which means that it can be either true or false . while(!showShip) means that the while loop should keep looping (repeating) as long as the value of showShip is false .

Answer 2

while(!showShip) // don't get this while loop

Using ! inverts the boolean , so the loop condition is a short way of saying

while(showShip == false) // This is the long way

Of course in order to exit the loop you need to set showShip to true , but the body of your loop never does it. Therefore, the loop is infinite . Most likely, the intention has been to do

System.out.println("\n" +" BOOM!");
showShip = true;

Note: A short way to write "continue while a variable is true is

while (showShip) // skip the == true part