Source Code : ComoboBox loads and saves items automatically from a file

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ComoboBox loads and saves items automatically from a file

  

import java.awt.BorderLayout;
import java.awt.Cursor;
import java.awt.Dimension;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyAdapter;
import java.awt.event.KeyEvent;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import java.awt.event.WindowListener;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.ObjectInput;
import java.io.ObjectInputStream;
import java.io.ObjectOutput;
import java.io.ObjectOutputStream;
import java.net.URL;

import javax.swing.Box;
import javax.swing.BoxLayout;
import javax.swing.ComboBoxModel;
import javax.swing.JComboBox;
import javax.swing.JEditorPane;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextField;
import javax.swing.event.HyperlinkEvent;
import javax.swing.event.HyperlinkListener;

public class MemComboBoxDemo extends JFrame {

  protected MemComboBox urlComboBox = new MemComboBox();

  public MemComboBoxDemo() {
    super();
    setSize(300, 100);
    getContentPane().setLayout(new BorderLayout());

    JPanel p = new JPanel();
    p.setLayout(new BoxLayout(p, BoxLayout.X_AXIS));
    p.add(new JLabel("Address"));

    urlComboBox.load("addresses.dat");
    ComboBoxListener lst = new ComboBoxListener();
    urlComboBox.addActionListener(lst);

    MemComboAgent agent = new MemComboAgent(urlComboBox);

    p.add(urlComboBox);
    getContentPane().add(p, BorderLayout.NORTH);

    WindowListener wndCloser = new WindowAdapter() {
      public void windowClosing(WindowEvent e) {
        urlComboBox.save("addresses.dat");
        System.exit(0);
      }
    };
    addWindowListener(wndCloser);

    setVisible(true);
    urlComboBox.grabFocus();
  }

  class ComboBoxListener implements ActionListener{
    public void actionPerformed(ActionEvent evt) {
      System.out.println( urlComboBox.getSelectedItem());
    }
  }

  public static void main(String argv[]) {
    new MemComboBoxDemo();
  }
}

class MemComboAgent extends KeyAdapter {
  protected JComboBox comboBox;

  protected JTextField editor;

  public MemComboAgent(JComboBox c) {
    comboBox = c;
    editor = (JTextField) c.getEditor().getEditorComponent();
    editor.addKeyListener(this);
  }

  public void keyReleased(KeyEvent e) {
    char ch = e.getKeyChar();
    if (ch == KeyEvent.CHAR_UNDEFINED || Character.isISOControl(ch))
      return;
    int pos = editor.getCaretPosition();
    String str = editor.getText();
    if (str.length() == 0)
      return;

    for (int k = 0; k < comboBox.getItemCount(); k++) {
      String item = comboBox.getItemAt(k).toString();
      if (item.startsWith(str)) {
        editor.setText(item);
        editor.setCaretPosition(item.length());
        editor.moveCaretPosition(pos);
        break;
      }
    }
  }
}

class MemComboBox extends JComboBox {
  public static final int MAX_MEM_LEN = 30;

  public MemComboBox() {
    super();
    setEditable(true);
  }

  public void add(String item) {
    removeItem(item);
    insertItemAt(item, 0);
    setSelectedItem(item);
    if (getItemCount() > MAX_MEM_LEN)
      removeItemAt(getItemCount() - 1);
  }

  public void load(String fName) {
    try {
      if (getItemCount() > 0)
        removeAllItems();
      File f = new File(fName);
      if (!f.exists())
        return;
      FileInputStream fStream = new FileInputStream(f);
      ObjectInput stream = new ObjectInputStream(fStream);

      Object obj = stream.readObject();
      if (obj instanceof ComboBoxModel)
        setModel((ComboBoxModel) obj);

      stream.close();
      fStream.close();
    } catch (Exception e) {
      System.err.println("Serialization error: " + e.toString());
    }
  }

  public void save(String fName) {
    try {
      FileOutputStream fStream = new FileOutputStream(fName);
      ObjectOutput stream = new ObjectOutputStream(fStream);

      stream.writeObject(getModel());

      stream.flush();
      stream.close();
      fStream.close();
    } catch (Exception e) {
      System.err.println("Serialization error: " + e.toString());
    }
  }
}

           
         
    
  

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