Java: How to count the no. of lines in a file? [duplicate]

Answer 1

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)
            {
            }
        }
    }
}

Answer 2

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++;
}

Answer 3

    BufferedReader reader = null;
    try { 
        reader = new BufferedReader(new FileReader(filename));
        long count = 0;
        while ((line = reader.readLine()) != null) {
            count++;
        }
    } catch (Exception e) {
         // do something
    }

Answer 4

You can use a BufferedReader to read complete lines or a LineNumberReader which does the counting itself.

Answer 5

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()
}

Answer 6

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();
}