布尔真或假

Question

public class Main {
    public static void main(String[] args) {
        boolean b = false;
        b = true;

        boolean toBe = false;
        b = toBe || !toBe;
        if (b) {
            System.out.println(toBe);
        }



    }

I saw this code online while trying to learn boolean and the output of this is false. Can someone please explain to me how why is the output false? Thank you

Answer 1

You set "b" to false and then changed it to true, so "b" is true. Then you set "toBe" to false. The next line does nothing, it returns true but doesn't assign it to anything. Then you check if "b" equals true, and it does. So then you print out "toBe" which equals false. That is why false is printed.

Hope this helps!!

Answer 2

|| is the logical or operator. It returns true if at least one operator is true. It's truth table looks like this:

a b a || b
1 1   1
1 0   1
0 1   1
0 0   0

Which means that b will be true, and thus the block within the if statement will execute. And it outputs "false" since that's the value of toBe .

Answer 3

since boolean toBe = false;

b=toBe || !toBe 
b = false || !fasle
b = false || true 
b = true

so b is true which means

System.out.println(toBe); // prints false since tobBE is false

PLEASE: see truth table for short circuit logical or ||

True || x = True
false || True = True
false || Flase = false

x -> is a don't care ie either true or false