liquibase-core/src/main/java/liquibase/database/core/H2Database.java
private String getConcatSql(List<String> values) {
        if (values.size() == 1) {
            return values.get(0);
        } else {
            return START_CONCAT + values.get(0) + SEP_CONCAT + getConcatSql(values.subList(1, values.size())) + END_CONCAT;
        }
    }
private String getConcatSql(List<String> values) {
        if (values.size() == 1) {
            return values.get(0);
        } else {
            return START_CONCAT + values.get(0) + SEP_CONCAT + getConcatSql(values.subList(1, values.size())) + END_CONCAT;
        }
    }
Recursive way of building CONCAT instruction

@param values a non null List of String
@return a String containing the CONCAT instruction with all elements, or only a value if there is only one element in the list