Reported by Bhaktavatsal R Maram at http://mail.openjdk.java.net/pipermail/core-libs-dev/2018-April/052799.html

This issue is continuation to bug 8201540 (Extend the set of supported charsets in java.base on AIX) in which we have moved default charsets of most of the locales supported by Operating System to java.base module thus enabling OpenJDK on those locales for AIX platform.

As part of that, charsets for locales Ja_JP (IBM-943) and Zh_TW (big5) also have been moved. However, corresponding charsets mapped in Java is not correct for them on AIX. Following are the details:

1. IBM-943 [1] for locale Ja_JP should be mapped to IBM-943C [2]

Fundamental difference between IBM-943 and IBM-943C is that IBM-943C is ASCII compatible which means code points 'yen' and 'overline' of IBM-943 is replaced with 'backslash' and 'tilde' from ASCII character set.


2. Big5 for locale Zh_TW should be mapped to IBM-950 [3]

I've attached simple test program to print the default charset along with fix for this issue. When run test program (PrintDefaultCharset) with IBM JDK 8 (on AIX) for locales Ja_JP & Zh_TW, following is output.

-bash-4.4$ LANG=Ja_JP ~/JDKs/IBM/80/ON/sdk/jre/bin/java PrintDefaultCharset
LANG = Ja_JP
Default charset = x-IBM943C
file.encoding = IBM-943C
sun.jnu.encoding = IBM-943C

-bash-4.4$ LANG=Zh_TW ~/JDKs/IBM/80/ON/sdk/jre/bin/java PrintDefaultCharset
LANG = Zh_TW
Default charset = x-IBM950
file.encoding = IBM-950
sun.jnu.encoding = IBM-950


Same test run with openJDK 11 gives following output

-bash-4.4$ LANG=Ja_JP ~/jdk/bin/java PrintDefaultCharset
LANG = Ja_JP
Default charset = x-IBM943
file.encoding = IBM-943
sun.jnu.encoding = IBM-943

-bash-4.4$ LANG=Zh_TW ~/jdk/bin/java PrintDefaultCharset
LANG = Zh_TW
Default charset = Big5
file.encoding = big5
sun.jnu.encoding = big5

Following is the test  program to reproduce the problem:

import java.nio.charset.*;
class PrintDefaultCharset {
     public static void main(String[] args) {
        System.out.println("LANG = "+System.getenv("LANG"));
        System.out.println("Default charset = "+Charset.defaultCharset().name());
        System.out.println("file.encoding = "+System.getProperty("file.encoding"));
        System.out.println("sun.jnu.encoding = "+System.getProperty("sun.jnu.encoding"));
     }
}