What is the difference between while (x = false) and while (!x) in Java?

Question

Sorry, I'm new to Java, so this question might be unclear. I have been recently dealing with enclosing a try and catch statement in a while loop, because I wanted to make sure that getting input was enclosed from the rest of the program. I have come across a problem where using an exclamation mark (!) in front of a variable in the while conditions (e.g. while (!done)) instead of using = false (e.g. while (done = false)) changes the way my program runs. The former (!done) results in the try and except statements running as expected. The latter (done = false) does not, simply skipping them and moving on to the next part of the code. I was under the impression that ! before a variable meant the same thing as var = false. Am I mistaken? Here's an example: ``` import java.util.Scanner; public class TestOne { public static void main(String args[]) { Scanner input = new Scanner(System.in); int num; boolean inputDone = false; while (!inputDone) { try { System.out.print("Enter in a number here…

Accepted Answer

Note the difference between `done = false` and `done == false`. The first one assigns `done` to be `false` and evaluates as `false`, the second one compares `done` with `false` and is exactly identical to `!done`.

So if you use:

```
while (done = false)
{
 // code here
}
```

Then `done` is set to `false` and the code within the while loop doesn't run at all.

What is the difference between while (x = false) and while (!x) in Java?

Solution

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