Typecasting Component object to JComboBox is throwing warnings

I am using HashMap to store Swing GUI components (labels, text fields, combo box and more). So to store all types of these components in the HashMap, I have defined its type as "Component" which is an upper class in Swing inheritance hierarchy. But I am getting a warning from the compiler as below:

Flower.java:36: warning: [unchecked] unchecked cast
                JComboBox<String> cmbProfCourseNo = (JComboBox<String>) formComponents.get("myComboBox");
                                                                                          ^
  required: JComboBox<String>
  found:    Component

There is no problem in execution and functionality of the program. One way to solve this is to store the components by declaring the HashMap of their type (like JLabel HashMap for labels, JComboBox HashMap for combo boxes and so on). But I want to store all the kinds in a single HashMap. So my query is cannot we typecast Component objects as JComboBox or any other down-level Swing components based on the inheritance hierarchy?

Below is my source code:

import java.awt.Component;
import javax.swing.JFrame;
import javax.swing.JComboBox;
import javax.swing.JComponent;
import javax.swing.DefaultComboBoxModel;
import java.util.Map;
import java.util.HashMap;


class Flower 
{   
    //declare the frame
    private JFrame frame;

    //declare HashMap
    private Map<String, JComponent> formComponents= new HashMap<String, JComponent>();

    //main method of the class 
    public static void main(String[] args) {
        new Flower().init();
    }

    public void init() {
        frame = new JFrame("Flower");
        frame.setSize(650, 725);
        frame.setLayout(null);

        formComponents.put("myComboBox", new JComboBox<String>());
        formComponents.get("myComboBox").setBounds(125, 165, 200, 25);
        frame.add(formComponents.get("myComboBox"));
        frame.setVisible(true);

        //update comboBox
        updateComboBox((JComboBox<String>) formComponents.get("myComboBox"));

        //get comboBox
        JComboBox<String> cmbProfCourseNo = (JComboBox<String>) formComponents.get("myComboBox");
    }


    public void updateComboBox(JComboBox<String> comboBox) {        
        DefaultComboBoxModel<String> model = (DefaultComboBoxModel<String>) comboBox.getModel();        
        model.addElement("Car");
        //set the model
        comboBox.setModel(model);
    }
}