Reading and Displaying Text Files

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

@SuppressWarnings("serial")
public class isuru extends Frame implements ActionListener{
 String directory;
 TextArea textarea;
 
 public isuru(){
  this(null, null);
 }
 
 public isuru(String filename){
  this(null, filename);
 }
 
 public isuru(String directory, String filename){
  super();
  
  addWindowListener(new WindowAdapter(){
   public void windowClosing(WindowEvent e){
    dispose();
   }
  });
  
  textarea = new TextArea("", 24, 80);
  textarea.setFont(new Font("MonoSpaced", Font.PLAIN, 12));
  textarea.setEditable(false);
  this.add("Center", textarea);
  
  Panel p = new Panel();
  p.setLayout(new FlowLayout(FlowLayout.RIGHT, 10, 5));
  this.add(p, "South");
  
  Font font = new Font("SansSerif", Font.BOLD, 14);
  Button openfile = new Button("Open File");
  Button close = new Button("Close");
  openfile.addActionListener(this);
  openfile.setActionCommand("open");
  openfile.setFont(font);
  
  close.addActionListener(this);
  close.setActionCommand("close");
  close.setFont(font);
  p.add(openfile);
  p.add(close);
  
  this.pack();
  
  if(directory == null){
   File f;
   if((filename != null) && (f = new File(filename)).isAbsolute()){
    directory = f.getParent();
    filename = f.getName();
   }else{
    directory = System.getProperty("user.dir");
   }
   
   this.directory = directory;
   setFile(directory, filename);
  }
 }
 
 public void setFile(String directory, String filename){
  if((filename == null) || filename.length() == 0)
   return;
  File f;
  FileReader in = null;
  try{
   f = new File(directory, filename);
   in = new FileReader(f);
   char[] buffer = new char[4096];
   int len;
   textarea.setText("");
   while((len = in.read(buffer)) != -1){
    String s = new String(buffer,0,len);
    textarea.append(s);
   }
   this.setTitle("FileViewer: "+filename);
   textarea.setCaretPosition(0);
  }catch(IOException e){
   textarea.setText(e.getClass().getName()+ ": " + e.getMessage( ));
   this.setTitle("FileViewer: "+filename+ ": I/O Exception");
  }finally{
   try{
    if(in != null)
     in.close();
   }catch(IOException e){
   
   }
  }
 }
 
 public void actionPerformed(ActionEvent e){
  String cmd = e.getActionCommand();
  if(cmd.equals("open")){
   FileDialog f = new FileDialog(this, "Open File");
   f.setDirectory(directory);
   
   f.show();
   
   directory = f.getDirectory();
   setFile(directory, f.getFile());
   f.dispose();
  }
  else if(cmd.equals("close"))
   this.dispose();
 }
 
 public static void main(String args[]){
  Frame f = new isuru((args.length == 1)?args[0]:null);
  f.addWindowListener(new WindowAdapter(){
    public void windowClosed(WindowEvent e){
     System.exit(0);
    }
  });
  
  f.show();
 }

}