JCombobox Listener how to enable it when item is s

I have a JComboBox that displays Name From database Patients_Details

public void ComboItem() {

chooser.removeAllItems();
chooser.addItem("Please Select...");
try {   
         String sql="select * from Patients_Details";
         pst = conn.prepareStatement(sql);
         rs=pst.executeQuery();
        while (rs.next()) {
            String id = rs.getString("Patient_ID"); // Get the Id
            String name = rs.getString("Name"); // Get the Name 

            ComboItem comboItem = new ComboItem(id, name); // Create a new ComboItem
            chooser.addItem(comboItem); // Put it into the ComboBox
            String tmp=comboItem.getid();
        }
    } catch (SQLException sqle) {
        System.out.println(sqle);
    }
}

This is from comboitem class that only returns the name and not the id

  public String toString() {
    return this.name  ;
   }

My question is how do I get the selecteditem so that this action can be performed I have no clue how to do this I have been trying all bunch of code for almost 2 hours any help will be much appreciated

NB I am Java beginner

  private void chooserPopupMenuWillBecomeInvisible(javax.swing.event.PopupMenuEvent evt) {

    try{
      String sql="select * from Patients_Details where Patient_ID=? ";
      pst=conn.prepareStatement(sql);
      rs=pst.executeQuery();
      if(rs.next()){
      String add1=rs.getString("Patient_ID");
      txtpatientid.setText(add1);
      String add2=rs.getString("Name");
      txtname.setText(add2);
      String add3=rs.getString("Age");
      txtage.setText(add3);
      String add4=rs.getString("Gender");
      txtgender.setText(add4);
      String add5=rs.getString("Date");
      txtdate.setText(add5);
       }
  }
  catch(Exception e) {
    JOptionPane.showMessageDialog(null,e ); 
  }
}

Simply add an ActionListener to the combo box. When actionPerformed is called, you can look up the selected value and call what ever methods you need to.

For example:

chooser.addActionListener(new ActionListener() {
    public void actionPerformed(ActionEvent evt) {
        Object selectedValue = chooser.getSelectedValue();
        // carry on with what ever you need
    }
});

Have a look at ...