如何比较两个在jsp中选择的arraylist和set选项？

Question

I have two tables:

Table 1 geoCountry with columns

country_name | country_code

Table 2 user_countries with columns

country_name | username 

I want to set users country pre-selected (ie fetching from db)

Here is code that I have tried

     <select multiple="multiple" class="country" style="width: 200px">
         <%
           sql6 = "SELECT DISTINCT countryname FROM user_countries WHERE username = ?";
           ps6 = connection.prepareStatement(sql6);
           ps6.setString(1, user);
           rs6 = ps6.executeQuery();

            while (rs6.next()) {
                usercountries.add(rs6.getString(1));
             }

            for (int i = 0; i < geoCountry.size(); i++) {
                 for (int j = 0; j < usercountries.size(); j++) {
                    if (usercountries.get(j).equals(geoCountry.get(i))) {
                 %>
                <option value="<%=geoCountry.get(i)%>" selected="selected"><%=geoCountry.get(i)%></option>
                 <% } else {%>
                 <option value="<%=geoCountry.get(i)%>"><%=geoCountry.get(i)%></option>
              <% }
              }
           } %>
      </select>

it is showing duplicated values in select box .. why?

Answer 1

Remove second cycle with " usercountries", thms. like:

  for (int i = 0; i < geoCountry.size(); i++) {
         if (usercountries.contains(geoCountry.get(i)) {
             %>
            <option value="<%=geoCountry.get(i)%>" selected="selected"><%=geoCountry.get(i)%></option>
             <% } else {%>
             <option value="<%=geoCountry.get(i)%>"><%=geoCountry.get(i)%></option>
          <% }
       } %>