On Japanese environment, following SHIFT_JIS compatible charsets are there:
* PCK (x-PCK)
* MS932 (windows-31j)
* IBM943C (x-IBM943C)
According to make/data/charsetmapping/charsets,
PCK and MS932 are independent charset and have no dependencies on others.

On RHEL8, SHIFT_JIS encoding is supported
======
$ env LANG=ja_JP.sjis locale charmap
SHIFT_JIS
======

According to make/data/charsetmapping/stdcs-linux,
SJIS (SHIFT_JIS) is in there, also MS932 and PCK are there.
This means these are in java.base module on Linux platform.
But IBM943C is not in stdcs-linux.
I think IBM943C also should be in java.base module because of compatibility.