int x = -555;
boolean isNegative = (x < 0);

if (isNegative)
{
x = 100;
if (isNegative)
System.out.println("no");
else
System.out.println("yes");
}
else
System.out.println("maybe");

why is the answer ''no'' and not ''yes''?
The boolean ignores x=100?

this is an assignment that only occurs once. the value stored here will stay until you re-assign it, regardless of the current value of x. if you want it to behave in such a way isNegative always looks at the current value of x, then you can create a method so it's re-evaluated every time it's called.