Here is a simple JMenuItem example in java swing through which you can perform open and save operations on File.

import java.io.*;
import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
import javax.swing.event.*;

public class SwingMenu{
    final JTextArea txtArea=new JTextArea(0,0); 
    JFrame frame = new JFrame();
    String Filename;
    String filename;
  public static void main(String[] args) {
  SwingMenu s = new SwingMenu();
  }
   void ReadFile()
         {
         BufferedReader d;
         StringBuffer sb = new StringBuffer();
         try
             {
             d = new BufferedReader(new FileReader(filename));
             String line;
             while((line=d.readLine())!=null)
             sb.append(line + "\n");
             txtArea.setText(sb.toString());
             d.close();
         }
         catch(FileNotFoundException fe)
             {
             System.out.println("File not Found");
         }
         catch(IOException ioe){}
     }

  public SwingMenu(){


   JScrollPane scroll=new JScrollPane(txtArea);
  frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
  JMenuBar menubar = new JMenuBar();
  JMenu filemenu = new JMenu("File");
  JMenuItem fileItem1 = new JMenuItem("Open");
  JMenuItem fileItem2 = new JMenuItem("Save");
  filemenu.add(fileItem1);
  filemenu.add(fileItem2);
  menubar.add(filemenu);

      fileItem1.addActionListener(new ActionListener(){
          public void actionPerformed(ActionEvent e)
             {
             FileDialog fd = new FileDialog(frame, "select File",FileDialog.LOAD);
             fd.show();
             if (fd.getFile()!=null)
                 {
                 filename = fd.getDirectory() + fd.getFile();
                 frame.setTitle(filename);
                 ReadFile();
             }
             txtArea.requestFocus();
         }
      });


      fileItem2.addActionListener(new ActionListener(){
           public void actionPerformed(ActionEvent e)
             {
             FileDialog fd = new FileDialog(frame,"Save File",FileDialog.SAVE);
             fd.show();
             if (fd.getFile()!=null)
                 {
                 filename = fd.getDirectory() + fd.getFile();
                 frame.setTitle(filename);
                 try
                     {
                     DataOutputStream d = new DataOutputStream(new FileOutputStream(filename));
                     String line = txtArea.getText();
                     BufferedReader br = new BufferedReader(new StringReader(line));
                     while((line = br.readLine())!=null)
                         {
                         d.writeBytes(line + "\r\n");

                     }
                     d.close();
                 }
                 catch(Exception ex)
                     {
                     System.out.println("File not found");
                 }
                 txtArea.requestFocus();
             }
         }
          });

  frame.setJMenuBar(menubar);
  frame.add(txtArea);
  frame.setSize(400,400);
  frame.setVisible(true);
  }
}

Here is a simple JMenuItem example in java swing through which you can perform open and save operations on File.

import java.io.*;
import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
import javax.swing.event.*;

public class SwingMenu{
    final JTextArea txtArea=new JTextArea(0,0); 
    JFrame frame = new JFrame();
    String Filename;
    String filename;
  public static void main(String[] args) {
  SwingMenu s = new SwingMenu();
  }
   void ReadFile()
         {
         BufferedReader d;
         StringBuffer sb = new StringBuffer();
         try
             {
             d = new BufferedReader(new FileReader(filename));
             String line;
             while((line=d.readLine())!=null)
             sb.append(line + "\n");
             txtArea.setText(sb.toString());
             d.close();
         }
         catch(FileNotFoundException fe)
             {
             System.out.println("File not Found");
         }
         catch(IOException ioe){}
     }

  public SwingMenu(){


   JScrollPane scroll=new JScrollPane(txtArea);
  frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
  JMenuBar menubar = new JMenuBar();
  JMenu filemenu = new JMenu("File");
  JMenuItem fileItem1 = new JMenuItem("Open");
  JMenuItem fileItem2 = new JMenuItem("Save");
  filemenu.add(fileItem1);
  filemenu.add(fileItem2);
  menubar.add(filemenu);

      fileItem1.addActionListener(new ActionListener(){
          public void actionPerformed(ActionEvent e)
             {
             FileDialog fd = new FileDialog(frame, "select File",FileDialog.LOAD);
             fd.show();
             if (fd.getFile()!=null)
                 {
                 filename = fd.getDirectory() + fd.getFile();
                 frame.setTitle(filename);
                 ReadFile();
             }
             txtArea.requestFocus();
         }
      });


      fileItem2.addActionListener(new ActionListener(){
           public void actionPerformed(ActionEvent e)
             {
             FileDialog fd = new FileDialog(frame,"Save File",FileDialog.SAVE);
             fd.show();
             if (fd.getFile()!=null)
                 {
                 filename = fd.getDirectory() + fd.getFile();
                 frame.setTitle(filename);
                 try
                     {
                     DataOutputStream d = new DataOutputStream(new FileOutputStream(filename));
                     String line = txtArea.getText();
                     BufferedReader br = new BufferedReader(new StringReader(line));
                     while((line = br.readLine())!=null)
                         {
                         d.writeBytes(line + "\r\n");

                     }
                     d.close();
                 }
                 catch(Exception ex)
                     {
                     System.out.println("File not found");
                 }
                 txtArea.requestFocus();
             }
         }
          });

  frame.setJMenuBar(menubar);
  frame.add(txtArea);
  frame.setSize(400,400);
  frame.setVisible(true);
  }
}