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

public class FileOrganizer extends JFrame implements ActionListener
{
    public static final int WIDTH = 400;
    public static final int HEIGHT = 300;
    public static final int NUMBER_OF_CHAR = 30;

    private JTextField fileNameField;
    private JTextField firstLineField;

    public static void main(String[] args)
    {
        FileOrganizer gui = new FileOrganizer();
        gui.setVisible(true);
    }

    public FileOrganizer( )
    {
        setSize(WIDTH, HEIGHT);
        WindowDestroyer listener = new WindowDestroyer( );
        addWindowListener(listener);
        Container contentPane = getContentPane( );
        contentPane.setLayout(new FlowLayout( ));

        JButton showButton = new JButton("Show first line");
        showButton.addActionListener(this);
        contentPane.add(showButton);

        JButton removeButton = new JButton("Remove file");
        removeButton.addActionListener(this);
        contentPane.add(removeButton);

        JButton resetButton = new JButton("Reset");
        resetButton.addActionListener(this);
        contentPane.add(resetButton);

        fileNameField = new JTextField(NUMBER_OF_CHAR);
        contentPane.add(fileNameField);
        fileNameField.setText("Enter file name here.");

        firstLineField = new JTextField(NUMBER_OF_CHAR);
        contentPane.add(firstLineField);
    }
    
    public void actionPerformed(ActionEvent e)
    {
       String actionCommand = e.getActionCommand( );

       if (actionCommand.equals("Show first line"))
           showFirstLine();
       else if (actionCommand.equals("Remove file"))
           removeFile();
       else if (actionCommand.equals("Reset"))
       {
           fileNameField.setText("Enter file name here.");
           firstLineField.setText("");
       }
       else
           firstLineField.setText("Unexpected error.");
    }

    public void showFirstLine()
    {
        BufferedReader fileInput;
        String firstLine;
        String fileName = fileNameField.getText();
        File fileObject = new File(fileName);

        if ( ! fileObject.exists( ))
            firstLineField.setText("No such file");
        else if ( ! fileObject.canRead( ))
            firstLineField.setText("That file is not readable.");
        else
        {
            try
            {
               fileInput =
                     new BufferedReader(new FileReader(fileObject));
               firstLine = fileInput.readLine( );
               firstLineField.setText(firstLine);
               fileInput.close( );
           }
           catch(IOException e)
           {
              firstLineField.setText("Problem reading from file.");
           }
        }
    }

    public void removeFile()
    {
        BufferedReader fileInput;
        String firstLine;
        String fileName = fileNameField.getText();
        File fileObject = new File(fileName);

        if ( ! fileObject.exists( ))
            firstLineField.setText("No such file");
        else if ( ! fileObject.canWrite( ))
            firstLineField.setText("Permission denied.");
        else
        {
            if (fileObject.delete())
                firstLineField.setText("File deleted.");
            else
                firstLineField.setText("Could not delete file.");
        }
    }
}