Remove particular Item

1. /*
2.         Remove Particular Item From AWT Choice Or Combobox Example
3.         This java example shows how to remove a particular item of a choice or
4.         a combobox control using remove method of AWT Choice class.
5. */
6.  
7. import java.applet.Applet;
8. import java.awt.Choice;
9.  
10. /*
11. <applet code="RemoveItemExample" width=200 height=200>
12. </applet>
13. */
14.  
15.  
16. public class RemoveItemExample extends Applet{
17.  
18.         Choice language = null;
19.        
20.         public void init(){
21.                
22.                 //create choice or combobox
23.                 language = new Choice();
24.                
25.                 //add items to the choice
26.                 language.add("Java");
27.                 language.add("C++");
28.                 language.add("VB");
29.                 language.add("Perl");
30.                
31.                 //add choice or combobox
32.                 add(language);
33.                
34.                 /*
35.                  * To remove an item from a choice or combobox, use
36.                  * void remove(int index) or
37.                  * void remove(String item) method of AWT Choice class.
38.                  */
39.                
40.                 language.remove(1);
41.                 /*
42.                  * You can also use language.remove("C++")
43.                  */
44.         }
45. }

get Slected item

1. /*
2.         Get Selected Item Of AWT Choice Or Combobox Example
3.         This java example shows how to get selected item of a choice or combobox
4.         using Java AWT Choice class.
5. */
6.  
7. import java.applet.Applet;
8. import java.awt.Choice;
9. import java.awt.Graphics;
10. import java.awt.event.ItemEvent;
11. import java.awt.event.ItemListener;
12.  
13. /*
14. <applet code="GetSelectedItemExample" width=200 height=200>
15. </applet>
16. */
17.  
18. public class GetSelectedItemExample extends Applet implements ItemListener{
19.  
20.         Choice language = null;
21.        
22.         public void init(){
23.                
24.                 //create choice or combobox
25.                 language = new Choice();
26.                
27.                 //add items to the choice
28.                 language.add("Java");
29.                 language.add("C++");
30.                 language.add("VB");
31.                 language.add("Perl");
32.                
33.                 //add choice or combobox
34.                 add(language);
35.                
36.                 //add item listener
37.                 language.addItemListener(this);
38.                
39.         }
40.        
41.         public void paint(Graphics g){
42.                 /*
43.                  * To get selected item, use
44.                  * String getSelectedItem()
45.                  * method of AWT Choice class.
46.                  */
47.                 g.drawString(language.getSelectedItem(),10, 70);
48.         }
49.  
50.         public void itemStateChanged(ItemEvent arg0) {
51.                 repaint();             
52.         }
53. }

selectItem Example

package awt;

import java.applet.Applet;
import java.awt.Choice;

/*
<applet code="SelectItemExample" width=200 height=200>
</applet>
*/

public class SelectItemExample extends Applet{
      
        Choice language = null;
      
        public void init(){
              
                //create choice or combobox
                language = new Choice();
              
                //add items to the choice
                language.add("Java");
                language.add("C++");
                language.add("VB");
                language.add("Perl");
              
                //add choice or combobox
                add(language);
              
                /*
                 * To select an item from a choice or combobox, use
                 * void select(int index) or
                 * void select(String item) method of AWT Choice class.
                 */
              
                language.select(1);
                /*
                 * You can also use language.select("C++")
                 */
        }
}

TimeMachine

import java.applet.Applet;
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.List;
import java.awt.Panel;
import java.awt.event.ItemEvent;
import java.awt.event.ItemListener;
import java.io.File;
import java.io.FileNotFoundException;
import java.util.Arrays;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.Scanner;
import java.util.Set;

public class TimeMachine extends Applet implements ItemListener{
    private static final long serialVersionUID = 1L;

    private List listRegion = new List();
    private List listSubRegion = new List();
    private Map<String, Set<String>> regionCountryMap = new HashMap<String, Set<String>>();

    public void init()
    {
        setLayout(new BorderLayout());

        getLocationInfo();
        Panel buttons = new Panel(new BorderLayout());
        buttons.setBackground(Color.cyan);
        buttons.add(listRegion, BorderLayout.WEST);
        buttons.add(listSubRegion, BorderLayout.CENTER);
        add(buttons, BorderLayout.NORTH);
    }

    private void getLocationInfo() {
        String fileName = "e:\\regions.csv";
        File file = new File(fileName);
        try {
            Scanner inputStream = new Scanner(file);
            inputStream.useDelimiter(System.getProperty("line.separator"));
            listRegion = new List();
            while (inputStream.hasNext())
            {
                String data = inputStream.next(); // gets the whole line
                String[] arrayLocations = data.split(",");
                if(arrayLocations.length != 2){
                    System.out.println("Invalid entry in file : "+ Arrays.toString(arrayLocations));
                    continue;
                }
                String region = arrayLocations[0];
                if(!regionCountryMap.containsKey(region))
                {
                    listRegion.add(region);
                    regionCountryMap.put(region, new HashSet<String>());
                }
                regionCountryMap.get(region).add(arrayLocations[1]);//Set handles duplicates as well
            }
            inputStream.close();
            System.out.println("Region, Country list has been parsed successfully");
            listRegion.addItemListener(this);
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        }
    }

    @Override
    public void itemStateChanged(ItemEvent e) {
        Set<String> countries = regionCountryMap.get(listRegion.getSelectedItem());
        listSubRegion.removeAll();
        for(String country : countries) {
            listSubRegion.add(country);
        }
        listSubRegion.validate();
        listSubRegion.repaint();
    }
}