JDBC sum two columns and display the result in third column

import java.sql.*;
public class DatabaseExample
{
    public static void main(String[]args){
try{
Class.forName("com.mysql.jdbc.Driver");
Connection con = DriverManager.getConnection("jdbc:mysql://localhost:3306/test","root","root");
Statement st=con.createStatement();
Statement st1=con.createStatement();
ResultSet rs=st.executeQuery("select * from sum");
while(rs.next()){
    int id=rs.getInt("id");
int sum=rs.getInt("col1")+rs.getInt("col2");
st1.executeUpdate("update sum set col3="+sum+" where id="+id+"");
}
Statement stmt=con.createStatement();
ResultSet rs1=stmt.executeQuery("select * from sum");
while(rs1.next()){
    System.out.println(rs1.getInt("col1")+"\t "+rs1.getInt("col2")+"\t "+rs1.getInt("col3"));
}
}
catch(Exception e){
System.out.println(e);
}
    }
}