age >= 21 && age <= 35
In most situations, the operands of AND can be in either order. The following
age >= 21 && age <= 35
is the equivalent of this:
age <= 35 && age >= 21
One false is enough to make the entire expression false, regardless of where the false occurs.
Warning: If a boolean expression includes an assignment operator or method calls, then the order sometimes does matter. The reason for this involves the short-circuit optimization mentioned previously. Mostly you don't need to worry about this, but make a mental note about this potential problem.
Chapter 40 describes this situation in detail. For the examples in this chapter, the order of operands does not matter.
Examine this expression:
( Monster.isAlive() && (hitpoints = Hero.attack()) < 50 )
Do you suspect that the order of operands in this expression matters?