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Closed 8 years ago.
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Number of lines in a file in Java
I need to count the number of lines of a txt file that is passed to java through a command line argument. I know how to read from a file but i am having trouble doing the rest. any help would be appreciated.
here is what i have so far:
import java.util.*;
import java.io.*;
public class LineCounter {
public static void main (String [] args) throws IOException{
Scanner file = new Scanner(new File("myFlile.txt"));
int count = 0;
while(file.hasNext()){
boolean s = file.hasNext();
int count = file.nextInt();
}
System.out.println(count);
}
}
Why are you pulling nextInt() and saving hasNext() inside the loop? If you are in there, you already know another line exists, so why not do something like:
while (file.hasNextLine()) {
count++;
file.nextLine();
}
You should check javadoc for the java.util.Scanner class: http://download.oracle.com/javase/6/docs/api/java/util/Scanner.html
Scanner has methods hasNextLine and nextLine that you can use for this. hasNextLine() checks if there are still lines in the files and nextLine() reads one line from the file. Using those methods you get an algorithm like this:
let the amount of lines be 0
as long as there are lines left in file
read one line and go to the next line
increment amount of lines by 1
Your code could be something like this
int count = 0;
while(file.hasNextLine())
{
count++;
file.nextLine()
}
You can do it this way:
FileInputStream fstream = new FileInputStream("filename");
BufferedReader br = new BufferedReader(new InputStreamReader(fstream));
String strLine;
int count = 0;
while ((strLine = br.readLine()) != null) {
count++;
}
BufferedReader reader = null;
try {
reader = new BufferedReader(new FileReader(filename));
long count = 0;
while ((line = reader.readLine()) != null) {
count++;
}
} catch (Exception e) {
// do something
}
I wrote a little project analyser, some time ago. It's not really an answer, but I wanted to share my solution. There is no main() method yet. Just create one like this:
MainFrame mf = new MainFrame();
mf.setVisible(true);
It supports for filtering files on file extensions. So you can specify for example C++. This will accept all .h and .cpp files.
You have to specify a folder and it will recursively count files, lines and bytes.
import java.awt.event.ItemEvent;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileFilter;
import java.io.FileReader;
import javax.swing.DefaultComboBoxModel;
import javax.swing.JButton;
import javax.swing.JFileChooser;
import javax.swing.JOptionPane;
import javax.swing.SwingWorker;
import javax.swing.filechooser.FileNameExtensionFilter;
/**
*
* @author martijncourteaux
*/
public class MainFrame extends javax.swing.JFrame
{
private File root;
private volatile int _files;
private volatile int _lines;
private volatile long _bytes;
/** Creates new form MainFrame */
public MainFrame()
{
initComponents();
}
/** This method is called from within the constructor to
* initialize the form.
* WARNING: Do NOT modify this code. The content of this method is
* always regenerated by the Form Editor.
*/
@SuppressWarnings("unchecked")
// <editor-fold defaultstate="collapsed" desc="Generated Code">//GEN-BEGIN:initComponents
private void initComponents() {
jLabel1 = new javax.swing.JLabel();
btnSelectRoot = new javax.swing.JButton();
lblRoot = new javax.swing.JLabel();
cmbExtensions = new javax.swing.JComboBox();
jLabel2 = new javax.swing.JLabel();
btnAnalyse = new javax.swing.JButton();
setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
setTitle("Project Analyser");
setLocation(new java.awt.Point(40, 62));
jLabel1.setText("Project Root:");
btnSelectRoot.setText("Select");
btnSelectRoot.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
btnSelectRootActionPerformed(evt);
}
});
lblRoot.setText(" ");
cmbExtensions.setModel(new javax.swing.DefaultComboBoxModel(new String[] { "[Any]", "h;cpp", "java", "xml", "Customize..." }));
cmbExtensions.addItemListener(new java.awt.event.ItemListener() {
public void itemStateChanged(java.awt.event.ItemEvent evt) {
cmbExtensionsItemStateChanged(evt);
}
});
jLabel2.setText("Extensions:");
btnAnalyse.setText("Analyse");
btnAnalyse.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
btnAnalyseActionPerformed(evt);
}
});
org.jdesktop.layout.GroupLayout layout = new org.jdesktop.layout.GroupLayout(getContentPane());
getContentPane().setLayout(layout);
layout.setHorizontalGroup(
layout.createParallelGroup(org.jdesktop.layout.GroupLayout.LEADING)
.add(layout.createSequentialGroup()
.addContainerGap()
.add(layout.createParallelGroup(org.jdesktop.layout.GroupLayout.LEADING)
.add(cmbExtensions, 0, 352, Short.MAX_VALUE)
.add(org.jdesktop.layout.GroupLayout.TRAILING, layout.createSequentialGroup()
.add(jLabel1)
.addPreferredGap(org.jdesktop.layout.LayoutStyle.RELATED)
.add(lblRoot, org.jdesktop.layout.GroupLayout.DEFAULT_SIZE, 174, Short.MAX_VALUE)
.addPreferredGap(org.jdesktop.layout.LayoutStyle.RELATED)
.add(btnSelectRoot))
.add(jLabel2)
.add(btnAnalyse, org.jdesktop.layout.GroupLayout.DEFAULT_SIZE, 352, Short.MAX_VALUE))
.addContainerGap())
);
layout.setVerticalGroup(
layout.createParallelGroup(org.jdesktop.layout.GroupLayout.LEADING)
.add(layout.createSequentialGroup()
.addContainerGap()
.add(layout.createParallelGroup(org.jdesktop.layout.GroupLayout.BASELINE)
.add(jLabel1)
.add(btnSelectRoot)
.add(lblRoot))
.add(18, 18, 18)
.add(jLabel2)
.addPreferredGap(org.jdesktop.layout.LayoutStyle.RELATED)
.add(cmbExtensions, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE, org.jdesktop.layout.GroupLayout.DEFAULT_SIZE, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE)
.addPreferredGap(org.jdesktop.layout.LayoutStyle.UNRELATED)
.add(btnAnalyse, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE, 90, org.jdesktop.layout.GroupLayout.PREFERRED_SIZE)
.addContainerGap(org.jdesktop.layout.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))
);
pack();
}// </editor-fold>//GEN-END:initComponents
private void btnSelectRootActionPerformed(java.awt.event.ActionEvent evt)//GEN-FIRST:event_btnSelectRootActionPerformed
{//GEN-HEADEREND:event_btnSelectRootActionPerformed
JFileChooser fc = new JFileChooser(root.getParentFile());
fc.setFileSelectionMode(JFileChooser.DIRECTORIES_ONLY);
int option = fc.showDialog(this, "Select");
if (option == JFileChooser.APPROVE_OPTION)
{
this.root = fc.getSelectedFile();
this.lblRoot.setText(root.getParentFile().getName() + "/" + root.getName());
}
}//GEN-LAST:event_btnSelectRootActionPerformed
private void cmbExtensionsItemStateChanged(java.awt.event.ItemEvent evt)//GEN-FIRST:event_cmbExtensionsItemStateChanged
{//GEN-HEADEREND:event_cmbExtensionsItemStateChanged
if (cmbExtensions.getSelectedIndex() == cmbExtensions.getItemCount() - 1 && evt.getStateChange() == ItemEvent.SELECTED)
{
evt.getStateChange();
String extensions = JOptionPane.showInputDialog(this, "Specify the extensions, seperated by semi-colon (;) and without dot.");
if (extensions == null)
{
cmbExtensions.setSelectedIndex(0);
return;
}
DefaultComboBoxModel model = (DefaultComboBoxModel) cmbExtensions.getModel();
model.insertElementAt(extensions, cmbExtensions.getSelectedIndex());
cmbExtensions.validate();
cmbExtensions.setSelectedIndex(cmbExtensions.getItemCount() - 2);
}
}//GEN-LAST:event_cmbExtensionsItemStateChanged
private void btnAnalyseActionPerformed(java.awt.event.ActionEvent evt)//GEN-FIRST:event_btnAnalyseActionPerformed
{//GEN-HEADEREND:event_btnAnalyseActionPerformed
if (root == null)
{
JOptionPane.showMessageDialog(this, "Please select a root.");
return;
}
_files = 0;
_lines = 0;
_bytes = 0L;
btnAnalyse.setHorizontalAlignment(JButton.LEFT);
updateButtonText();
final int i = cmbExtensions.getSelectedIndex();
final String[] extensions = cmbExtensions.getSelectedItem().toString().toLowerCase().split(";");
final FileFilter ff = new FileFilter()
{
@Override
public boolean accept(File file)
{
if (i == 0) return true;
if (file.isDirectory())
{
return true;
}
String name = file.getName().toLowerCase();
for (String ext : extensions)
{
if (name.endsWith(ext))
{
return true;
}
}
return false;
}
};
final SwingWorker<Void, Void> sw = new SwingWorker<Void, Void>()
{
@Override
protected Void doInBackground() throws Exception
{
scan(root, ff);
updateButtonText();
return null;
}
};
sw.execute();
final SwingWorker<Void, Void> sw2 = new SwingWorker<Void, Void>()
{
@Override
protected Void doInBackground() throws Exception
{
while (!sw.isDone())
{
updateButtonText();
}
return null;
}
};
sw2.execute();
}//GEN-LAST:event_btnAnalyseActionPerformed
// Variables declaration - do not modify//GEN-BEGIN:variables
private javax.swing.JButton btnAnalyse;
private javax.swing.JButton btnSelectRoot;
private javax.swing.JComboBox cmbExtensions;
private javax.swing.JLabel jLabel1;
private javax.swing.JLabel jLabel2;
private javax.swing.JLabel lblRoot;
// End of variables declaration//GEN-END:variables
private void updateButtonText()
{
String txt = "<html>";
txt += "Files: " + _files + "<br>\n";
txt += "Lines: " + _lines + "<br>\n";
txt += "Bytes: " + _bytes + "\n";
btnAnalyse.setText(txt);
}
private void scan(File folder, FileFilter ff)
{
File[] files = folder.listFiles(ff);
try
{
for (File f : files)
{
if (f == null)
{
continue;
}
if (f.isDirectory())
{
scan(f, ff);
} else
{
analyse(f);
}
}
} catch (Exception e)
{
}
}
private void analyse(File f)
{
if (f.exists())
{
_files++;
_bytes += f.length();
try
{
BufferedReader r = new BufferedReader(new FileReader(f));
while (r.readLine() != null)
{
_lines++;
}
r.close();
} catch (Exception e)
{
}
}
}
}
You can use a BufferedReader to read complete lines or a LineNumberReader which does the counting itself.
