JAVA MYSQL gui form error loading data

I have created to tables in mysql A with 1 column(and is primary key) and table B with 2 column(both primary key but one is pk of table A i.e foreign key) I want to create 2 jcombobox eg A and B so that when i select value in combobox A only values stored with A is shown in jcombobox eg If i select state mumbai it should only show the cities of mumbai I am trying this code Connection myconnection;

 String path="jdbc:mysql://localhost/";
 String place="start";
 String username="root";
 String password="";
 try{

 myconnection=DriverManager.getConnection(path+place, username, password);
 try{
     String query="Select * from state1 where states1=?";
     PreparedStatement mystatement=myconnection.prepareStatement(query);

      mystatement.setString(1, jComboBox1.getSelectedItem().toString());
     ResultSet myresult=mystatement.executeQuery();
     if(myresult.next())
     {
        do{
            jComboBox1.addItem(myresult.getString("state"));
        }
        while(myresult.next());
                }     


 }

I have stored some data in database table A but its not displaying in table B so i am unable to store data in table B.