//Imports are listed in full to show what's being used
//could just import javax.swing.* and java.awt.* etc..
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JComboBox;
import javax.swing.JButton;
import javax.swing.JLabel;
import javax.swing.JList;
import java.awt.BorderLayout;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;

public class GuiApp1 {
 
 //Note: Typically the main method will be in a
 //separate class. As this is a simple one class
 //example it's all in the one class.
 public static void main(String[] args) {
 
 new GuiApp1();
 }

 public GuiApp1()
 {
 JFrame guiFrame = new JFrame();
 
 //make sure the program exits when the frame closes
 guiFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
 guiFrame.setTitle("Example GUI");
 guiFrame.setSize(300,250);
 
 //This will center the JFrame in the middle of the screen
 guiFrame.setLocationRelativeTo(null);
 
 //Options for the JComboBox 
 String[] fruitOptions = {"Apple", "Apricot", "Banana"
 ,"Cherry", "Date", "Kiwi", "Orange", "Pear", "Strawberry"};
 
 //Options for the JList
 String[] vegOptions = {"Asparagus", "Beans", "Broccoli", "Cabbage"
 , "Carrot", "Celery", "Cucumber", "Leek", "Mushroom"
 , "Pepper", "Radish", "Shallot", "Spinach", "Swede"
 , "Turnip"};
 
 //The first JPanel contains a JLabel and JCombobox
 final JPanel comboPanel = new JPanel();
 JLabel comboLbl = new JLabel("Fruits:");
 JComboBox fruits = new JComboBox(fruitOptions);
 
 comboPanel.add(comboLbl);
 comboPanel.add(fruits);
 
 //Create the second JPanel. Add a JLabel and JList and
 //make use the JPanel is not visible.
 final JPanel listPanel = new JPanel();
 listPanel.setVisible(false);
 JLabel listLbl = new JLabel("Vegetables:");
 JList vegs = new JList(vegOptions);
 vegs.setLayoutOrientation(JList.HORIZONTAL_WRAP);
 
 listPanel.add(listLbl);
 listPanel.add(vegs);
 
 JButton vegFruitBut = new JButton( "Fruit or Veg");
 
 //The ActionListener class is used to handle the
 //event that happens when the user clicks the button.
 //As there is not a lot that needs to happen we can 
 //define an anonymous inner class to make the code simpler.
 vegFruitBut.addActionListener(new ActionListener()
 {
 @Override
 public void actionPerformed(ActionEvent event)
 {
 //When the fruit of veg button is pressed
 //the setVisible value of the listPanel and
 //comboPanel is switched from true to 
 //value or vice versa.
 listPanel.setVisible(!listPanel.isVisible());
 comboPanel.setVisible(!comboPanel.isVisible());

 }
 });
 
 //The JFrame uses the BorderLayout layout manager.
 //Put the two JPanels and JButton in different areas.
 guiFrame.add(comboPanel, BorderLayout.NORTH);
 guiFrame.add(listPanel, BorderLayout.CENTER);
 guiFrame.add(vegFruitBut,BorderLayout.SOUTH);
 
 //make sure the JFrame is visible
 guiFrame.setVisible(true);
 }
 
}