Use the JAVA_CHARSET_MAPPING connection property to supersede the default Adaptive Server character set mapping.
props.put("CHARSET", "cp949"); /* Server character set */ props.put("JAVA_CHARSET_MAPPING", "ms949"); /* Java character set mapping */
Most of the Adaptive Server character sets have the same name as the Java character sets that they are mapped to. See Supported Character Sets for those character sets that are mapped to a Java character set with a different name.