Assigning values in while condition

Question

First of all I know what is difference between = and ==. I want to use = to implicitly make infinite loop. So my code looks like this:

 boolean flag= true;
    while (flag=false){
        System.out.println("inside loop");
    }
    System.out.println("rest");

Unfortunately it doesn't enter the loop and prints "rest". Why? Am I reading this wrong? In while condition I am assigning value false to flag. So it loops while flag=false (which is).

And when I do this(changed from false to true) it enters infinite loop:

boolean flag= true;
    while (flag=true){
        System.out.println("inside loop");
    }
    System.out.println("rest");

In my opinion both of these examples should enter the loop. But only the 1st one does. Please help me understand this. Thanks

Answer 1

This is due to the way assignment operators works.

In your loop condition you are stating

flag = true

Which returns true, but before that is assigns true to flag

This is because we are allowed do multiple assignments at once like this:

boolean test = flag = true;
// test == true

essentially (flag = true) translates to:

• assign true to flag
• return true for further use