Question

可能重复：
Number of lines in a file in Java

我需要计算通过命令行参数传递给java的txt文件的行数。我知道如何从文件中读取，但我在完成剩下的工作时遇到了麻烦。任何帮助，将不胜感激。这是我到目前为止所做的：

   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);
   }
     }

Answer 1

为什么要在循环中拉nextInt()并保存hasNext()？如果你在那里，你已经知道另一条线存在，那么为什么不这样做：

while (file.hasNextLine()) {
  count++;
  file.nextLine();
}

Answer 2

您应该检查java.util.Scanner类的javadoc：http://download.oracle.com/javase/6/docs/api/java/util/Scanner.html

Scanner具有可用于此的方法hasNextLine和nextLine。 hasNextLine（）检查文件中是否还有行，nextLine（）从文件中读取一行。使用这些方法可以获得如下算法：

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

您的代码可能是这样的

int count = 0;
while(file.hasNextLine())
{
    count++;
    file.nextLine()
}

Answer 3

你可以这样做：

FileInputStream fstream = new FileInputStream("filename");
BufferedReader br = new BufferedReader(new InputStreamReader(fstream));
String strLine;
int count = 0;
while ((strLine = br.readLine()) != null)   {
  count++;
}

Answer 4

    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 5

前段时间我写了一个小项目分析器。这不是一个真正的答案，但我想分享我的解决方案。还没有main()方法。只需创建一个这样的：

MainFrame mf = new MainFrame();
mf.setVisible(true);

它支持过滤文件扩展名上的文件。所以你可以指定例如C ++。这将接受所有.h和.cpp个文件。

您必须指定一个文件夹，它将以递归方式计算文件，行和字节。

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 6

您可以使用BufferedReader来读取完整的行或LineNumberReader进行计数本身。

Java：如何计算不。文件中的行？

6 个答案: