age >= 21 && age <= 35

Either Order (usually)

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.

One of the next chapters describes this situation in detail. For the examples in this chapter, the order of operands does not matter.

( Monster.isAlive() && (hitpoints = Hero.attack()) < 50 )