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Java File IO & NIO2

without comments

Java 6, or the* package which has been around a long time has known limits. There are some noted issues with the Java 6* package, and why I wrote the file back in 2002. The class creates a series of static methods that let you read, write, copy, and move files both locally and across the network.

  • Many methods fail to throw exceptions
  • A number of simple methods are missing, like the copy and move methods
  • There isn’t any support for symbolic links
  • Many methods fail to scale with large files

The Java 7 introduces the java.nio.file.* package, and it does the following:

  • Works more consistently across platforms
  • Provides improved access to more file attributes
  • Provides improved exception handling
  • Supports non-native file systems

A student asked me to post the file. So, I posted it on the site. I hope it helps simplifies the use of File IO operations. Admittedly, it’s easier to read and write a file with Java 7. The following provides a complete example class:

import java.awt.Dimension;
import java.awt.Font;
import java.nio.file.*;
import java.nio.charset.Charset;
import javax.swing.JOptionPane;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
public class ReadWriteFile {
    // Constructor for objects of class ReadFile
    public ReadWriteFile() {}
  // Write a file.
  public static void writeFile(String fileName, String fileText) {
    // Declare a file path.
    Path p = Paths.get(fileName);
    // Write a file.
    try {
      BufferedWriter bw =
        Files.newBufferedWriter( p, Charset.forName("ISO-8859-1")
                                  , StandardOpenOption.CREATE, StandardOpenOption.APPEND );
      bw.write(fileText, 0, fileText.length());
      bw.close(); }
    catch(IOException ioe) {
      System.out.println("Error writing a file."); 
      System.exit(0); }}
  // Read a file.
  public static String readFile(String fileName) {
    // Declare a String to hold the file.
    String text = "", line = "";
    // Declare a file path.
    Path p = Paths.get(fileName);
    // Write a file.
    try {
      // Read the file.
      BufferedReader fileInput =
      // Read and process first line.
      line = fileInput.readLine();
      text = line + "\n";
      // Read and process second thru last lines.
      while (line != null) {
        line = fileInput.readLine();
        if (line != null)
          text += line + "\n"; }
      // Close the file input.
      fileInput.close(); }
    catch(EOFException eofe) {
        System.out.println("No more lines to read.");
        System.exit(0); }
    catch(IOException ioe) {
        System.out.println("Error reading file."); 
        System.exit(0); }
    // Return a String value.
    return text;
  // Declare a static main to read a text file.
  public static void main(String[] args) {
    // Declare local object types.
    JOptionPane op = new JOptionPane();
    JScrollPane sp;
    JTextArea ta;
    Object[] options = {};
    // Instantiate a test class.
    ReadWriteFile rwf = new ReadWriteFile();
    // Text the readFile method.
    if (args.length > 0) {
      // Set the value and formatting of the text area.
      ta = new JTextArea(rwf.readFile(args[0]));
      ta.setFont(new Font(Font.SANS_SERIF,Font.PLAIN,14));
      // Assign the text area to a scroll pane.
      sp = new JScrollPane(ta);
      sp.setPreferredSize(new Dimension(400,200));
      // Invoke a generic option pane.
      op.showOptionDialog(null, sp, "File Content", JOptionPane.DEFAULT_OPTION, JOptionPane.PLAIN_MESSAGE, null, options, null); }
    // Test the writeFile method.  
    if (args.length > 1) {
      rwf.writeFile(args[1],rwf.readFile(args[0])); }

You can call it like this to read and write an output.txt file from any directory:

java ReadWriteFile Fellowship.txt output.txt

It will display a JOptionDialog like this:


Any suggestions or improvements are welcome.

Written by maclochlainn

May 18th, 2014 at 12:31 pm

Posted in Java,Java 7

Tagged with , ,