// how hard is it to simply read from a (text) file?
// 
// last modified: 11-2-00
//			      

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

public class TryReadFromFile
{
        public static void main(String args[])
        {
                TryReadFromFileFrame thisFrame = new TryReadFromFileFrame();

		thisFrame.setSize(600, 400);
        
		thisFrame.setTitle("Trying to Simply Read From a File");
		thisFrame.show();
        }
}

class TryReadFromFileFrame extends JFrame implements ActionListener
{	
	JLabel			title, fileToReadLabel;
	JTextArea		fileContents, filesList;
	JScrollPane		fileContentsPane, filesListPane;
	JTextField 		fileToReadField;

	String			currentDirectory;
	File			currDirFile; 

	public TryReadFromFileFrame()
        {
		Container	myContentPane;

		myContentPane = getContentPane();
		myContentPane.setLayout(new FlowLayout());
                
		// gracefully handle a window closing event                      
                addWindowListener(new WindowAdapter()
                        {
                                public void windowClosing(WindowEvent e)
                                {
									System.exit(0);
                                }
                        });

		// this text area will hold names of files in current
		// directory 
		filesList = new JTextArea(10, 20);
		// if I put this JTextArea into a JScrollPane
		// in this way, then
		// the scroll pane will add scroll bars when
		// needed...!
		filesListPane = new JScrollPane(filesList);
		myContentPane.add(filesListPane);

		// here's how you can get the name of
		// the current working directory!
		currentDirectory = System.getProperty("user.dir");
		System.out.println("currentDirectory: " + currentDirectory);

		// get File object for current directory
		currDirFile = new File(currentDirectory);

		// this local method gets the files in currDirFile and
		// displays them in a JTextArea one
		// file name per line
		fillFilesList(currDirFile, filesList);

		// this text area will hold contents of the desired
		// file (within a scrollable JScrollPane)
		fileContents = new JTextArea(10, 20);
		fileContentsPane = new JScrollPane(fileContents);
		myContentPane.add(fileContentsPane);

		fileToReadLabel = new JLabel("type new file name: ");				
		myContentPane.add(fileToReadLabel);

		fileToReadField = new JTextField(20);
		fileToReadField.addActionListener(this);
		myContentPane.add(fileToReadField);
        }

	//-----
	// display the names of files in the directory corresponding
	// to currDir in the text area currFilesList
	//-----
	private void fillFilesList(File currDir, JTextArea currFilesList)
	{
		String		fileNamesToPrint;
		String[] 	filesInCurrDir;

		// what are the names of the files in
		// the current directory, at this point?
		filesInCurrDir = currDir.list(); 
			
		// put each in a string, each followed by a
		// newline character
		fileNamesToPrint = "";
		for (int i = 0; i < filesInCurrDir.length; i++)
		{
			fileNamesToPrint += filesInCurrDir[i] + "\n";
		}

		// make that the parameter text area's contents
		currFilesList.setText(fileNamesToPrint);	
	}

	// when a file name is entered into textfield,
	// either complain or read file contents into
	// fileContents textarea 
	public void actionPerformed(ActionEvent e)
	{
		String				fileToReadName, contentsString, 
							latestLine;
		File				fileToRead;
		// another java.io option... made for reading text in
		// particular (as opposed to binary files), permits
		// reading of a whole line at a time
		BufferedReader		fromStream;

		fileToReadName = fileToReadField.getText();

		fileToRead = new File(fileToReadName);

		// is this currently the name of an existing, readable file 
		// in the current directory? No good if not!
		if ((!fileToRead.exists())||(!fileToRead.canRead())||(!fileToRead.isFile()))
		{
			fileToReadField.setText("try again --- file " + 	
				fileToReadName + " cannot be read");
		}
		else
		{
			try
			{
				// instantiate FileReader stream fromStream,
				// use its readln() method to grab contents
				// to go into fileContents
				//
				// do not forget to close the file!
				fromStream = new BufferedReader(new FileReader(fileToRead));
				latestLine = fromStream.readLine();
				while (latestLine != null)
				{
					// hey! there's an append() method
					// to append to a text area!
					fileContents.append(latestLine + "\n");
					latestLine = fromStream.readLine();
				}					

				// is this "dangerous", not placing in a
				// finally clause or something?
				fromStream.close();
				fileToReadField.setText("");
			}
			catch (FileNotFoundException exc)
			{
				// a failed opening of a file (a failed attempt
				// to instantiate fromStream, above) could
				// throw a FileNotFoundException
				System.out.println("TryReadFromFile: Could not open: "
					+ fileToReadName);
			}
			catch (IOException exc)
			{
				System.out.println("TryReadFromFile: IOError: " +
					exc.getMessage());
			}
		}
	}
}