private boolean isHighSurrogate(final int ch) {
        return (SURROGATE1_MIN <= ch && ch <= SURROGATE1_MAX);
    }
Test whether the given character is a high surrogate

@param ch The character to test.
@return true if the character is the first character in a surrogate pair
stroom-pipeline/src/main/java/stroom/pipeline/xml/util/XMLWriter.java