import java.sql.*;
import java.util.*;
class GetRepeatedValuesFromDatabase 
{
    public static <T> List getDuplicate(Collection<T> list) {

    final List<T> l = new ArrayList<T>();
    Set<T> set = new HashSet<T>() {
    public boolean add(T e) {
        if (contains(e)) {
            l.add(e);
        }
        return super.add(e);
    }
   };
   for (T t : list){
        set.add(t);
    }
    return l;
}

public static <T> boolean hasDuplicate(Collection<T> list) {
    if(getDuplicate(list).isEmpty())
        return false;
    return true;
}
    public static void main(String[] args) 
    {
        ArrayList<String> list=new ArrayList<String>();

    try{
            Class.forName("com.mysql.jdbc.Driver");
           Connection con = DriverManager.getConnection("jdbc:mysql://localhost:3306/test", "root", "root");
           Statement st=con.createStatement();
           ResultSet rs=st.executeQuery("select * from data");
           String name;
           while(rs.next()){
              list.add(rs.getString("name"));

           }
           if(hasDuplicate(list)){
            List l=getDuplicate(list);
            for(int i=0;i<l.size();i++){
                System.out.println(l.get(i).toString());
            }
        }
    }
    catch(Exception e){}

    }
}