The problem of occupying space in Chinese

java development environment:
UTF-8 environment: Chinese characters account for 3 bytes, while char type occupies only one byte. Why is the following assignment method correct? (shouldn"t it be beyond the scope of char?)

char c = "";
Mar.10,2021
A char in

Java uses the Unicode code set, which takes up two bytes, and a Chinese character is also two bytes, so the char in Java can represent a Chinese character.

MySQL Query : SELECT * FROM `codeshelper`.`v9_news` WHERE status=99 AND catid='6' ORDER BY rand() LIMIT 5
MySQL Error : Disk full (/tmp/#sql-temptable-64f5-1e924b5-5c1e2.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
MySQL Errno : 1021
Message : Disk full (/tmp/#sql-temptable-64f5-1e924b5-5c1e2.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
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