Starting VM with "-Duser.country=CN -Duser.language=zh” as default locale.
According to the Locale.getDisplayName​() spec the values in parentheses should be comma separated:
http://download.java.net/java/jdk10/docs/api/java/util/Locale.html#getDisplayName()

However for the following example

Locale locale = new Locale("lll", "CCC", "VVV");
System.out.println("Locale.getDefault() = " + Locale.getDefault());
System.out.println("locale.getDisplayName() = " + locale.getDisplayName());

I get

Locale.getDefault() = zh_CN
locale.getDisplayName() = lll (CCC、VVV)

and (with default locale)

Locale.getDefault() = en_GB
locale.getDisplayName() = lll (CCC, VVV)

(see the difference in the used separator - it's comma v.s. '、')

Specification needs to be corrected.