Efficient way of reading a file

Question

how to read a file in an efficient way in java?? suggest any methods.. i used BufferedReader,which is very slow.. suggest any changes??

CODE:

import java.io.*;

import java.awt.; import javax.swing.; import java.awt.event.*; import java.lang.StringBuffer;

/The main class file starts here/

class TitleCaseRow10 extends JFrame implements ActionListener,FocusListener {

// Declare the required variables

JButton jbFileLoad,jbFileSave,jbCaseChange;
JLabel jlTitle,jlFileSelect,jlContentDisplay;
Font myFont;
JPanel mainPanel,fileOperationPanel,buttonPanel,fileOpenPanel;
JFrame jframe;
JTextField jtfFileName;
JTextArea jtaFileContent,jtaCaseChange;
JScrollPane jScrPaneContent,jScrPaneCaseChange;
boolean boolFileOk = false;
File file;
String fileName,strFileContent,strBuffer=""; 
JFileChooser fileChooser;

// Constructor method for TitleCaseRow10

TitleCaseRow10(String titleName)
{
 super(titleName);

}

void createAndShowGUI()

/*  This method is used to create the Graphical User Interface
    and show it in the screen.
    This method takes no input parameters 
    nor does it return any value.
*/

{

 // create and set up the window

 jframe = new JFrame();
 jframe.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
 jframe.setSize(500,600);

 // create the panels 
 // 1. mainPanel for containing other panels
 // 2. buttonPanel for containing buttons
 // 3. fileOpenPanel for containing file choose text filed
 //  and load file button
 // 4. fileOperationPanel for containing all the file operation objects

 mainPanel = new JPanel();
 buttonPanel = new JPanel();
 fileOperationPanel = new JPanel();
 fileOpenPanel = new JPanel();

 // create a file chooser
 fileChooser = new JFileChooser();

 // create labels and buttons

 jlTitle = new JLabel("TITLE CASE CHANGER",JLabel.CENTER);
 jlFileSelect = new JLabel("Enter the filename or click 'load file'");
 jlContentDisplay = new JLabel("TEXT DISPLAY AREAS",JLabel.CENTER);
 jbFileLoad = new JButton("Load File"); 
 jbFileSave = new JButton("Save File");
 jbCaseChange = new JButton("Title Case"); 

 //Create  text feild, text area and scroll panes

 jtfFileName = new JTextField(28);
 jtaFileContent = new JTextArea(30,10);
 jtaCaseChange = new JTextArea(30,10);
 jScrPaneContent = new JScrollPane(jtaFileContent);
 jScrPaneCaseChange = new JScrollPane(jtaCaseChange);


 // set up the panels

 fileOperationPanel.setBackground(Color.BLACK);
 fileOpenPanel.setBackground(Color.BLACK);
 buttonPanel.setBackground(Color.BLACK);
 mainPanel.setBackground(Color.BLACK);
 mainPanel.setLayout(new GridLayout(3,0,15,15));
 fileOperationPanel.setLayout(new GridLayout(5,0,5,5));
 fileOpenPanel.setLayout(new FlowLayout());
 buttonPanel.setLayout(new FlowLayout());

 // set up text field, labels and text area

 // set the font
 myFont = new Font("Constantia",1,15);
 jtfFileName.setFont(myFont);
 jlTitle.setFont(myFont);
 jlContentDisplay.setFont(myFont);
 jtaFileContent.setFont(myFont);
 jtaCaseChange.setFont(myFont);
 jlFileSelect.setFont(new Font("Arial",0,14));

 // set line wrap
 jtaFileContent.setLineWrap(true);
 jtaCaseChange.setLineWrap(true);

 //set foreground and background color
 jlTitle.setForeground(Color.WHITE);
 jlContentDisplay.setForeground(Color.WHITE);
 jlFileSelect.setForeground(Color.WHITE);
 jtaFileContent.setForeground(Color.LIGHT_GRAY);
 jtaCaseChange.setForeground(Color.LIGHT_GRAY);
 jtfFileName.setForeground(Color.LIGHT_GRAY);
 jtaFileContent.setBackground(Color.DARK_GRAY);  
 jtaCaseChange.setBackground(Color.DARK_GRAY);
 jtfFileName.setBackground(Color.DARK_GRAY);

 // Set default text to file content text area
 jtaFileContent.setText("Type text here");

 // set up scroll panes

 jScrPaneContent.setAutoscrolls(true);
 jScrPaneCaseChange.setAutoscrolls(true);
 jScrPaneCaseChange.getHorizontalScrollBar();
 jScrPaneCaseChange.getHorizontalScrollBar();

 // add the action listeners to buttons

 jbFileLoad.addActionListener(this);
 jbFileSave.addActionListener(this);
 jbCaseChange.addActionListener(this); 
 jtaFileContent.addFocusListener(this);

 // add all the components

 jframe.add(mainPanel);
 fileOpenPanel.add(jtfFileName);
 fileOpenPanel.add(jbFileLoad);
 buttonPanel.add(jbCaseChange);
 buttonPanel.add(jbFileSave);
 fileOperationPanel.add(jlTitle);
 fileOperationPanel.add(jlFileSelect);
 fileOperationPanel.add(fileOpenPanel);
 fileOperationPanel.add(buttonPanel);
 fileOperationPanel.add(jlContentDisplay);
 mainPanel.add(fileOperationPanel);
 mainPanel.add(jScrPaneContent);
 mainPanel.add(jScrPaneCaseChange);

 // set the frame visible

 jframe.setVisible(true);

}

public void actionPerformed(ActionEvent ae)
{
    String command = ae.getActionCommand();
    if(command.equals("Load File"))
    {
 System.out.println("Load File action");
 fileName = "";
 int retVal = fileChooser.showOpenDialog(this); 
 System.out.println("open dialog..."); 
 if(retVal==JFileChooser.APPROVE_OPTION)
 {
  try
  {
  file = fileChooser.getSelectedFile();
  fileName = fileChooser.getCurrentDirectory().getPath();
  fileName = fileName.concat("\\"+file.getName());
  jtfFileName.setText(fileName);
  boolFileOk=true;
  jtaFileContent.setText("");
  BufferedReader br= new BufferedReader(new FileReader(file),1000000);
  while((strFileContent = br.readLine())!=null)
      jtaFileContent.append(strFileContent+"\n");
  }
  catch(Exception e)
  {
  System.out.println("Some problem : "+e);
  }
 }

    }
    if(command.equals("Title Case"))
 System.out.println("Title Case action");
    if(command.equals("Save File"))
 System.out.println("Save File action");

}

public void focusGained(FocusEvent fe)
{
 System.out.println("Focus Gained");
 if(!boolFileOk)
 jtaFileContent.setText("");
}
public void focusLost(FocusEvent fe)
{

 System.out.println("Focus Lost");
}

/*

boolean loadFile(ActionEvent ae)
{

 // Check if the filename textfield is really empty

    if(jtfFileName.getText().trim().equals(""))

    {
 fileName = "";
 int retVal = fileChooser.showOpenDialog(TitleCaseRow10.this); 
 System.out.println("open dialog..."); 
 if(retVal==JFileChooser.APPROVE_OPTION)
 {
  try
  {
  file = fileChooser.getSelectedFile();
  fileName = fileChooser.getCurrentDirectory().getPath();
  fileName = fileName.concat("\\"+file.getName());
  jtfFileName.setText(fileName);
  return true;
  }
  catch(Exception e)
  {
   System.out.println("Some problem : "+e);
  }
 }
    }

    return false;
 // returns false if the filename is empty or 
 // if the file is not opened
}

*/


//*****************************************************************

//the main method which creates an 
//instance of the class R10TitleCase

//******************************************************************

public static void main(String args[])
{
 TitleCaseRow10 caseChanger = new TitleCaseRow10("Title Case");
 caseChanger.createAndShowGUI();
}

}

Answer 1

Define "efficient". It depends on your access pattern.

BufferedReader is going to speed things up when you read from the file one byte (or a few bytes) at a time, otherwise it's useless overhead. Still, it shouldn't be "very slow" unless you're doing something wrong in your code or have unrealistic expectations.

If you're reading very large files, java.nio, speficically FileChannel has much better performance than java.io.

Edit: You seem to be adding the file's contents to a JTextArea (I assume that's what jtaFileContent is) one line at a time - that's what's slow (because it has to update the UI every time, which involves a LOT of work), not the reading of the file. Instead, you should read all the text into a StringBuilder and only update the JTextArea once you have everything.

However, if your file is very large, you'll probably run out of memory and may have to look for a different UI component that loads only the part that is being shown; there should be something like that out there.

Answer 2

Are you sure it's actually the file IO which is slow? If you just append the same number of lines using a hard-coded string, is it fast? I wouldn't be surprised if it were the GUI which was slowing you down.

By the way, FileReader will use the platform default encoding, which is usually a bad idea. Use a FileInputStream and an InputStreamReader with a specific encoding. (Then wrap it in a BufferedReader of course.) You should also have a try/finally to close the reader at the end.

Answer 3

The problem is that you're appending directly into jtaFileContent. Try reading into a StringBuilder and then calling jtaFileContent.setText()

StringBuilder sb = new StringBuilder(100);
for(Scanner sc = new Scanner(new FileReader(fileName)); sc.hasNext(); )
  sb.append(sc.nextLine());

jtaFileContent.setText(sb.toString());