Should I use Java8/Guava Optional for every method that may return null?

Optional is used to represent nullable object, Some uses of this class include As a method return type, as an alternative to returning null to indicate that no value was available To distinguish between "unknown" (for example, not present in a map) and "known to have no value" (present in the map, with value Optional.absent()) To wrap nullable references for storage in a collection that does not s

[YuichiTanaka]

JavaのOptionalがどう役に立つか。