How to reuse a common panel?

I have a panel for adding an item to the cart. For example:

public class SomePanel extends JPanel {

	private static final long serialVersionUID = 1L;

	private JLabel firstLabel;
	private JLabel secondNameLabel;
	private JLabel thirdLabel;
	// and more..


	private JTextField firstTextField;
	private JTextField firstTextField;
	private JTextField thirdTextField;
	// and more..


	private void init() {
		firstLabel = new JLabel("First label");
		secondLabel = new JLabel("Second label");
		thirdLabel = new JLabel("Third label");		
		// and more..

		firstTextField = new JTextField("first field");
		secondTextField = new JTextField("second field");
		thirdTextField = new JTextField("third field");
		// and more..
	}

This panel is located in the dialog. When I select "Add" in the menu, a dialog and this panel appear. There I can enter information about the product and add the product.

The problem is that I have another three areas on the main form. These areas also display the same panel as above. How can I reuse an existing SomePanel and would this be a good practice? Maybe it's better to create singletons for each element (JLabel and JTextField) instead?
Maybe there is some special pattern for solving this problem?

It is an excellent suggestion to re-use the panel object, and it doesn't just work for a fixed number of fields, you can do it with a dynamic number of fields as well.

You have already created a wrapper around a JPanel, so we can simply add a method to it that will update the panel to display the new contents. In this case I have created a new method create(...) that will update the contents.

For example, if you have a fixed number of fields it might look something like this:

public class SomePanel extends JPanel {
private static final long serialVersionUID = 1L;
final int labelHeight = 10;
final int fieldHeight = 20;
private JLabel firstLabel = createLabel("label 1", 0, 0);
private JLabel secondLabel = createLabel("label 2", 0, 30);
private JLabel thirdLabel = createLabel("label 3", 0, 60);
// and more..
private JTextField firstTextField = createField(null, 0, 10);
private JTextField secondTextField = createField(null, 0, 40);
private JTextField thirdTextField = createField(null, 0, 70);
// and more..
//New method to udpate the contents
public boolean create(List<String> labels, List<String> textFields) {
if(labels.size() != textFields.size()){
System.out.println("Failed to update panel, there was a different number of labels and fields");
return false;
}
//Update the fixed label and field values
firstLabel.setText(labels.get(0));
secondLabel.setText(labels.get(1));
thirdLabel.setText(labels.get(2));
firstTextField.setText(textFields.get(0));
firstTextField.setText(textFields.get(1));
firstTextField.setText(textFields.get(2));
//Make sure that this panel is visiable after updating the values
this.setVisible(true);
//Success, return true
return true;
}
//Remove the x and y depending on the layout manager
private JLabel createLabel(String name, int x, int y){
//Create label
JLabel label = new JLabel(name);
//Set location and size or use a layour manager
label.setLocation(x, y);
label.setSize(50, labelHeight);
//Configure cutsom label settings
//label.setFont(...);
//label.setBorder(...);
//return the custom label
return label;
}
//Remove the x and y depending on the layout manager
private JTextField createField(String content, int x, int y) {
//Create label
JTextField field = new JTextField();
if(content != null){
field.setText(content);
}
//Set location and size or use a layour manager
field.setLocation(x, y);
field.setSize(80, fieldHeight);
//Configure cutsom text field settings
//field.setFont(...);
//field.setBorder(...);
//return the custom field
return field;
}
}

Or if you want to get fancy with dynamic content with a flexible number of labels and fields you could do something like this:

public class SomePanel extends JPanel {
private static final long serialVersionUID = 1L;
final int labelHeight = 10;
final int fieldHeight = 20;
final int padding = 5;
//Keep a list of contents only if you need to edit/retreive data from the panel
private List<JTextField> fieldList = new ArrayList<>();
//New method to udpate the contents
public boolean create(List<String> labels, List<String> textFields) {
if(labels.size() != textFields.size()){
System.out.println("Failed to update panel, there was a different number of labels and fields");
return false;
}
//remove previous components
this.removeAll();
//reset the dynamic lists (For if you need to edit/retreive data from the panel)
fieldList = new ArrayList<>();
//placement values (remove these if using a layout manager)
int xPos = 0;
int yPos = 0;
//Update the lists based on the new values
for (int count = 0; count < labels.size(); count++) {
//Create and add labels
JLabel dynamicLabel = createLabel(labels.get(count), xPos, yPos);
this.add(dynamicLabel);
//update placement location, remove if you use a layout manager
yPos += labelHeight + padding;
//Create and add fields
JTextField dynamicField = createField(textFields.get(count), xPos, yPos);
this.add(dynamicLabel);
//update placement location, remove if you use a layout manager
yPos += fieldHeight + padding;
//Store fields in a list so that we can retreive the contents later if needed, or if 
fieldList.add(dynamicField);
}
//Make sure that this panel is visiable after updating the values
this.setVisible(true);
//Success, return true
return true;
}
//Remove the x and y depending on the layout manager
private JLabel createLabel(String name, int x, int y){
//Create label
JLabel label = new JLabel(name);
//Set location and size or use a layour manager
label.setLocation(x, y);
label.setSize(50, labelHeight);
//Configure cutsom label settings
//label.setFont(...);
//label.setBorder(...);
//return the custom label
return label;
}
//Remove the x and y depending on the layout manager
private JTextField createField(String content, int x, int y) {
//Create label
JTextField field = new JTextField();
if(content != null){
field.setText(content);
}
//Set location and size or use a layour manager
field.setLocation(x, y);
field.setSize(80, fieldHeight);
//Configure cutsom text field settings
//field.setFont(...);
//field.setBorder(...);
//return the custom field
return field;
}
//Method to get the current field contents if needed or if edited by the user
public List<JTextField> getCurrentFieldContent (){
return fieldList;
}
}