programming-examples/java/Core_Java/Demonstrating the File class.java

Demonstrating the File class

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

public class FileTest extends JFrame implements ActionListener
     {
     private JTextField enter;
     private JTextArea output;
     public FileTest()
         {
         super( "Testing class File" );
        
         enter = new JTextField( "Enter file or directory name here" );
         enter.addActionListener( this );
         output = new JTextArea();
         Container c = getContentPane();
         ScrollPane p = new ScrollPane();
         p.add( output );
         c.add( enter, BorderLayout.NORTH );
         c.add( p, BorderLayout.CENTER );
        
         setSize( 400, 400 );
         show();
     }
    
     public void actionPerformed( ActionEvent e )
         {
         File name = new File( e.getActionCommand() );
        
         if ( name.exists() )
             {
             output.setText( name.getName() + " exists\n" + ( name.isFile() ? "is a file\n" :
             "is not a file\n" ) +
             ( name.isDirectory() ? "is a directory\n" :
             "is not a directory\n" ) +
             ( name.isAbsolute() ? "is absolute path\n" :
             "is not absolute path\n" ) +
             "Last modified: " + name.lastModified() +
             "\nLength: " + name.length() +
             "\nPath: " + name.getPath() +
             "\nAbsolute path: " + name.getAbsolutePath() +
             "\nParent: " + name.getParent() );
            
             if ( name.isFile() )
                 {
                 try
                     {
                     RandomAccessFile r = new RandomAccessFile( name, "r" );
                     StringBuffer buf = new StringBuffer();
                     String text;
                     output.append( "\n\n" );
                    
                     while( ( text = r.readLine() ) != null )
                     buf.append( text + "\n" );
                    
                     output.append( buf.toString() );
                 }
                 catch( IOException e2 )
                     {
                     JOptionPane.showMessageDialog( this, "FILE ERROR",
                     "FILE ERROR", JOptionPane.ERROR_MESSAGE );
                 }
             }
             else if ( name.isDirectory() )
                 {
                 String directory[] = name.list();
                
                 output.append( "\n\nDirectory contents:\n");
                
                 for ( int i = 0; i < directory.length; i++ )
                 output.append( directory[ i ] + "\n" );
             }
         }
         else
             {
             JOptionPane.showMessageDialog( this, e.getActionCommand() + " Does Not Exist",
             "FILE ERROR", JOptionPane.ERROR_MESSAGE );
         }
     }
    
     public static void main( String args[] )
         {
         FileTest app = new FileTest();
        
         app.addWindowListener( new WindowAdapter()
             {
             public void windowClosing( WindowEvent e )
                 {
                 System.exit( 0 );
             }
         } );
     }
}