+,- , ++, --
if( Double.isInfinite(z) || Double.isNan(z){
System.out.println("값 산출 불가");
}
== , != , > , >= , < , <=
&&,& , ||, | , ^, !
& , !, ^, ~
<< , >> , >>>
= , += , -=, = , /= , %= , = , !=, ^=, <<=, >>= , >>>=
score = 85;
(score > 90 ) ? "A" : (score > 80) ? "B":"C"
