It is anticipated that Unicode consortium will assign a code point for the Japanese new era square character.
http://blog.unicode.org/2018/09/new-japanese-era.html
JDK will need to accommodate this new code point in order to allow the code point in j.l.Character class, as well as return correct properties for the character, e.g., type == OTHER_SYMBOL. This issue will not cover the composition/decomposition of the new character, as it will be provided with the future ICU4J update (v63).