Java Tutorial/File/LineNumberReader

Compare text file line by line

   <source lang="java">

/*

• Copyright 2004 The Apache Software Foundation
• Licensed under the Apache License, Version 2.0 (the "License");
• you may not use this file except in compliance with the License.
• You may obtain a copy of the License at
• http://www.apache.org/licenses/LICENSE-2.0
• Unless required by applicable law or agreed to in writing, software
• distributed under the License is distributed on an "AS IS" BASIS,
• WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
• See the License for the specific language governing permissions and
• limitations under the License.
• /

//based on Apache technology http://www.apache.org import java.io.IOException; import java.io.LineNumberReader; import java.io.Reader; import java.util.List;

public class Diff {

   public static void readersAsText(Reader r1, String name1, Reader r2, String name2,
       List diffs)
       throws IOException
   {
       LineNumberReader reader1 = new LineNumberReader(r1);
       LineNumberReader reader2 = new LineNumberReader(r2);
       String line1 = reader1.readLine();
       String line2 = reader2.readLine();
       while (line1 != null && line2 != null)
       {
           if (!line1.equals(line2))
           {
               diffs.add("File \"" + name1 + "\" and file \"" +
                   name2 + "\" differ at line " + reader1.getLineNumber() +
                   ":" + "\n" + line1 + "\n" + line2);
               break;
           }
           line1 = reader1.readLine();
           line2 = reader2.readLine();
       }
       if (line1 == null && line2 != null)
           diffs.add("File \"" + name2 + "\" has extra lines at line " +
               reader2.getLineNumber() + ":\n" + line2);
       if (line1 != null && line2 == null)
           diffs.add("File \"" + name1 + "\" has extra lines at line " +
               reader1.getLineNumber() + ":\n" + line1);
   }

}</source>

Use LineNumberReader class to read file

   <source lang="java">

import java.io.File; import java.io.FileReader; import java.io.LineNumberReader; public class Main {

 public static void main(String[] args) throws Exception {
   File file = new File("data.csv");
   FileReader fr = new FileReader(file);
   LineNumberReader lnr = new LineNumberReader(fr);
   // lnr.setLineNumber(400);
   String line = "";
   while ((line = lnr.readLine()) != null) {
     System.out.println("Line Number " + lnr.getLineNumber() + ": " + line);
   }
   fr.close();
   lnr.close();
 }

}</source>

Using the LineNumberReader to read a text file line by line

   <source lang="java">

import java.io.FileReader; import java.io.LineNumberReader; public class Main {

 public static void main(String[] args) throws Exception {
   LineNumberReader r = new LineNumberReader(new FileReader("yourFile.txt"));
   String line = null;
   while ((line = r.readLine()) != null) {
     System.out.println(r.getLineNumber() + ": " + line);
   }
   r.close();
 }

}</source>