Java/File Input Output/BufferedReader

A simple FilterReader that strips HTML tags out of a stream of characters

   <source lang="java">
 

/*

* Copyright (c) 2004 David Flanagan.  All rights reserved.
* This code is from the book Java Examples in a Nutshell, 3nd Edition.
* It is provided AS-IS, WITHOUT ANY WARRANTY either expressed or implied.
* You may study, use, and modify it for any non-commercial purpose,
* including teaching and use in open-source projects.
* You may distribute it non-commercially as long as you retain this notice.
* For a commercial use license, or to purchase the book, 
* please visit http://www.davidflanagan.ru/javaexamples3.
*/

import java.io.BufferedReader; import java.io.FileReader; import java.io.FilterReader; import java.io.IOException; import java.io.Reader; /**

* A simple FilterReader that strips HTML tags (or anything between pairs of
* angle brackets) out of a stream of characters.
*/

public class RemoveHTMLReader extends FilterReader {

 /** A trivial constructor. Just initialize our superclass */
 public RemoveHTMLReader(Reader in) {
   super(in);
 }
 boolean intag = false; // Used to remember whether we are "inside" a tag
 /**
  * This is the implementation of the no-op read() method of FilterReader. It
  * calls in.read() to get a buffer full of characters, then strips out the
  * HTML tags. (in is a protected field of the superclass).
  */
 public int read(char[] buf, int from, int len) throws IOException {
   int numchars = 0; // how many characters have been read
   // Loop, because we might read a bunch of characters, then strip them
   // all out, leaving us with zero characters to return.
   while (numchars == 0) {
     numchars = in.read(buf, from, len); // Read characters
     if (numchars == -1)
       return -1; // Check for EOF and handle it.
     // Loop through the characters we read, stripping out HTML tags.
     // Characters not in tags are copied over previous tags
     int last = from; // Index of last non-HTML char
     for (int i = from; i < from + numchars; i++) {
       if (!intag) { // If not in an HTML tag
         if (buf[i] == "<")
           intag = true; // check for tag start
         else
           buf[last++] = buf[i]; // and copy the character
       } else if (buf[i] == ">")
         intag = false; // check for end of tag
     }
     numchars = last - from; // Figure out how many characters remain
   } // And if it is more than zero characters
   return numchars; // Then return that number.
 }
 /**
  * This is another no-op read() method we have to implement. We implement it
  * in terms of the method above. Our superclass implements the remaining
  * read() methods in terms of these two.
  */
 public int read() throws IOException {
   char[] buf = new char[1];
   int result = read(buf, 0, 1);
   if (result == -1)
     return -1;
   else
     return (int) buf[0];
 }
 /** The test program: read a text file, strip HTML, print to console */
 public static void main(String[] args) {
   try {
     if (args.length != 1)
       throw new IllegalArgumentException("Wrong number of args");
     // Create a stream to read from the file and strip tags from it
     BufferedReader in = new BufferedReader(new RemoveHTMLReader(new FileReader(args[0])));
     // Read line by line, printing lines to the console
     String line;
     while ((line = in.readLine()) != null)
       System.out.println(line);
     in.close(); // Close the stream.
   } catch (Exception e) {
     System.err.println(e);
     System.err.println("Usage: java RemoveHTMLReader$Test" + " <filename>");
   }
 }

}

 </source>
   
  
 
  

A standalone program that reads a list of classes and builds a database of packages, classes, and class fields and methods

   <source lang="java">
 

/*

* Copyright (c) 2004 David Flanagan.  All rights reserved.
* This code is from the book Java Examples in a Nutshell, 3nd Edition.
* It is provided AS-IS, WITHOUT ANY WARRANTY either expressed or implied.
* You may study, use, and modify it for any non-commercial purpose,
* including teaching and use in open-source projects.
* You may distribute it non-commercially as long as you retain this notice.
* For a commercial use license, or to purchase the book, 
* please visit http://www.davidflanagan.ru/javaexamples3.
*/

import java.io.BufferedReader; import java.io.FileInputStream; import java.io.FileReader; import java.lang.reflect.Field; import java.lang.reflect.Method; import java.lang.reflect.Modifier; import java.sql.Connection; import java.sql.DriverManager; import java.sql.PreparedStatement; import java.sql.SQLException; import java.sql.Statement; import java.util.ArrayList; import java.util.HashMap; import java.util.Map; import java.util.Properties; /**

* This class is a standalone program that reads a list of classes and builds a
* database of packages, classes, and class fields and methods.
*/

public class MakeAPIDB {

 public static void main(String args[]) {
   Connection c = null; // The connection to the database
   try {
     // Read the classes to index from a file specified by args[0]
     ArrayList classnames = new ArrayList();
     BufferedReader in = new BufferedReader(new FileReader(args[0]));
     String name;
     while ((name = in.readLine()) != null)
       classnames.add(name);
     // Now determine the values needed to set up the database
     // connection The program attempts to read a property file named
     // "APIDB.props", or optionally specified by args[1]. This
     // property file (if any) may contain "driver", "database", "user",
     // and "password" properties that specify the necessary values for
     // connecting to the db. If the properties file does not exist, or
     // does not contain the named properties, defaults will be used.
     Properties p = new Properties(); // Empty properties
     try {
       p.load(new FileInputStream(args[1])); // Try to load properties
     } catch (Exception e1) {
       try {
         p.load(new FileInputStream("APIDB.props"));
       } catch (Exception e2) {
       }
     }
     // Read values from Properties file
     String driver = p.getProperty("driver");
     String database = p.getProperty("database");
     String user = p.getProperty("user", "");
     String password = p.getProperty("password", "");
     // The driver and database properties are mandatory
     if (driver == null)
       throw new IllegalArgumentException("No driver specified!");
     if (database == null)
       throw new IllegalArgumentException("No database specified!");
     // Load the driver. It registers itself with DriverManager.
     Class.forName(driver);
     // And set up a connection to the specified database
     c = DriverManager.getConnection(database, user, password);
     // Create three new tables for our data
     // The package table contains a package id and a package name.
     // The class table contains a class id, a package id, and a name.
     // The member table contains a class id, a member name, and an bit
     // that indicates whether the class member is a field or a method.
     Statement s = c.createStatement();
     s.executeUpdate("CREATE TABLE package " + "(id INT, name VARCHAR(80))");
     s.executeUpdate("CREATE TABLE class " + "(id INT, packageId INT, name VARCHAR(48))");
     s.executeUpdate("CREATE TABLE member " + "(classId INT, name VARCHAR(48), isField BIT)");
     // Prepare some statements that will be used to insert records into
     // these three tables.
     insertpackage = c.prepareStatement("INSERT INTO package VALUES(?,?)");
     insertclass = c.prepareStatement("INSERT INTO class VALUES(?,?,?)");
     insertmember = c.prepareStatement("INSERT INTO member VALUES(?,?,?)");
     // Now loop through the list of classes and use reflection
     // to store them all in the tables
     int numclasses = classnames.size();
     for (int i = 0; i < numclasses; i++) {
       try {
         storeClass((String) classnames.get(i));
       } catch (ClassNotFoundException e) {
         System.out.println("WARNING: class not found: " + classnames.get(i) + "; SKIPPING");
       }
     }
   } catch (Exception e) {
     System.err.println(e);
     if (e instanceof SQLException)
       System.err.println("SQLState: " + ((SQLException) e).getSQLState());
     System.err.println("Usage: java MakeAPIDB " + "<classlistfile> <propfile>");
   }
   // When we"re done, close the connection to the database
   finally {
     try {
       c.close();
     } catch (Exception e) {
     }
   }
 }
 /**
  * This hash table records the mapping between package names and package id.
  * This is the only one we need to store temporarily. The others are stored in
  * the db and don"t have to be looked up by this program
  */
 static Map package_to_id = new HashMap();
 // Counters for the package and class identifier columns
 static int packageId = 0, classId = 0;
 // Some prepared SQL statements for use in inserting
 // new values into the tables. Initialized in main() above.
 static PreparedStatement insertpackage, insertclass, insertmember;
 /**
  * Given a fully-qualified classname, this method stores the package name in
  * the package table (if it is not already there), stores the class name in
  * the class table, and then uses the Java Reflection API to look up all
  * methods and fields of the class, and stores those in the member table.
  */
 public static void storeClass(String name) throws SQLException, ClassNotFoundException {
   String packagename, classname;
   // Dynamically load the class.
   Class c = Class.forName(name);
   // Display output so the user knows that the program is progressing
   System.out.println("Storing data for: " + name);
   // Figure out the packagename and the classname
   int pos = name.lastIndexOf(".");
   if (pos == -1) {
     packagename = "";
     classname = name;
   } else {
     packagename = name.substring(0, pos);
     classname = name.substring(pos + 1);
   }
   // Figure out what the package id is. If there is one, then this
   // package has already been stored in the database. Otherwise, assign
   // an id, and store it and the packagename in the db.
   Integer pid;
   pid = (Integer) package_to_id.get(packagename); // Check hashtable
   if (pid == null) {
     pid = new Integer(++packageId); // Assign an id
     package_to_id.put(packagename, pid); // Remember it
     insertpackage.setInt(1, packageId); // Set statement args
     insertpackage.setString(2, packagename);
     insertpackage.executeUpdate(); // Insert into package db
   }
   // Now, store the classname in the class table of the database.
   // This record includes the package id, so that the class is linked to
   // the package that contains it. To store the class, we set arguments
   // to the PreparedStatement, then execute that statement
   insertclass.setInt(1, ++classId); // Set class identifier
   insertclass.setInt(2, pid.intValue()); // Set package identifier
   insertclass.setString(3, classname); // Set class name
   insertclass.executeUpdate(); // Insert the class record
   // Now, get a list of all non-private methods of the class, and
   // insert those into the "members" table of the database. Each
   // record includes the class id of the containing class, and also
   // a value that indicates that these are methods, not fields.
   Method[] methods = c.getDeclaredMethods(); // Get a list of methods
   for (int i = 0; i < methods.length; i++) { // For all non-private
     if (Modifier.isPrivate(methods[i].getModifiers()))
       continue;
     insertmember.setInt(1, classId); // Set the class id
     insertmember.setString(2, methods[i].getName()); // Set method name
     insertmember.setBoolean(3, false); // It is not a field
     insertmember.executeUpdate(); // Insert into db
   }
   // Do the same thing for the non-private fields of the class
   Field[] fields = c.getDeclaredFields(); // Get a list of fields
   for (int i = 0; i < fields.length; i++) { // For each non-private
     if (Modifier.isPrivate(fields[i].getModifiers()))
       continue;
     insertmember.setInt(1, classId); // Set the class id
     insertmember.setString(2, fields[i].getName()); // Set field name
     insertmember.setBoolean(3, true); // It is a field
     insertmember.executeUpdate(); // Insert the record
   }
 }

}

 </source>
   
  
 
  

Call the static method PressAnykey to keep to "DOS" window open.

   <source lang="java">
 

import java.io.BufferedReader; import java.io.InputStreamReader; public class Main{

 public static void main(String[] args) {
   PressAnyKey();
 }
 public static void PressAnyKey() {
   BufferedReader input = new BufferedReader(new InputStreamReader(System.in));
   System.out.print("Press any key...");
   try {
     input.readLine();
   } catch (Exception e) {
     e.printStackTrace();
   }
 }

}

 </source>
   
  
 
  

Create BufferedReader from FileReader and Read / display lines from file

   <source lang="java">
 

import java.io.BufferedReader; import java.io.FileReader; class BufferedReaderDemo {

 public static void main(String args[]) throws Exception {
   FileReader fr = new FileReader(args[0]);
   // Create a buffered reader
   BufferedReader br = new BufferedReader(fr);
   // Read and display lines from file
   String s;
   while ((s = br.readLine()) != null)
     System.out.println(s);
   fr.close();
 }

}

 </source>
   
  
 
  

Create BufferedReader from InputStreamReader and System.in, read console input

   <source lang="java">
 

import java.io.BufferedReader; import java.io.InputStreamReader; class Main {

 public static void main(String args[]) throws Exception {
   InputStreamReader isr = new InputStreamReader(System.in);
   BufferedReader br = new BufferedReader(isr);
   while (true) {
     System.out.print("Radius? ");
     String str = br.readLine();
     double radius;
     try {
       radius = Double.valueOf(str).doubleValue();
     } catch (NumberFormatException nfe) {
       System.out.println("Incorrect format!");
       continue;
     }
     if (radius <= 0) {
       System.out.println("Radius must be positive!");
       continue;
     }
     System.out.println("radius " + radius);
     return;
   }
 }

}

 </source>
   
  
 
  

Create BufferedReader from StringReader

   <source lang="java">
 

import java.io.BufferedReader; import java.io.BufferedWriter; import java.io.FileReader; import java.io.FileWriter; import java.io.InputStreamReader; import java.io.PrintWriter; import java.io.StringReader; public class Main {

 public static void main(String[] args) throws Exception {
   BufferedReader stdin = new BufferedReader(new InputStreamReader(System.in));
   System.out.println(stdin.readLine());
   BufferedReader in = new BufferedReader(new FileReader("Main.java"));
   String s, s2 = new String();
   while ((s = in.readLine()) != null)
     s2 += s + "\n";
   in.close();
   StringReader in1 = new StringReader(s2);
   int c;
   while ((c = in1.read()) != -1)
     System.out.print((char) c);
   BufferedReader in2 = new BufferedReader(new StringReader(s2));
   PrintWriter out1 = new PrintWriter(new BufferedWriter(new FileWriter(
       "IODemo.out")));
   int lineCount = 1;
   while ((s = in2.readLine()) != null)
     out1.println(lineCount++ + ": " + s);
   out1.close();
 }

}

 </source>
   
  
 
  

Create BufferedReader from System.in

   <source lang="java">
 

import java.io.BufferedReader; import java.io.BufferedWriter; import java.io.InputStreamReader; import java.io.OutputStreamWriter; public class Main {

 public static void main(String[] args) throws Exception {
   BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
   String strLine = in.readLine();
   BufferedWriter out = new BufferedWriter(new OutputStreamWriter(System.out));
   out.write(strLine, 0, strLine.length());
   out.flush();
   in.close();
   out.close();
 }

}

 </source>
   
  
 
  

Create BufferedReader from URL

   <source lang="java">
 

import java.io.BufferedReader; import java.io.InputStreamReader; import java.net.URL; public class Main {

 public static void main(String[] args) throws Exception {
   URL url = new URL("http://localhost:1776");
   BufferedReader in = new BufferedReader(new InputStreamReader(url.openStream()));
   String line;
   while ((line = in.readLine()) != null) {
     System.out.println(line);
   }
   in.close();
 }

}

 </source>
   
  
 
  

Create BufferedReader out of FileReader

   <source lang="java">
 

/*

* Copyright (c) 1995 - 2008 Sun Microsystems, Inc.  All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
*   - Redistributions of source code must retain the above copyright
*     notice, this list of conditions and the following disclaimer.
*
*   - Redistributions in binary form must reproduce the above copyright
*     notice, this list of conditions and the following disclaimer in the
*     documentation and/or other materials provided with the distribution.
*
*   - Neither the name of Sun Microsystems nor the names of its
*     contributors may be used to endorse or promote products derived
*     from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
* IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
* THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER OR
* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/

import java.io.BufferedReader; import java.io.FileReader; import java.io.FileWriter; import java.io.IOException; import java.io.PrintWriter; public class CopyLines {

 public static void main(String[] args) throws IOException {
   BufferedReader inputStream = null;
   PrintWriter outputStream = null;
   try {
     inputStream = new BufferedReader(new FileReader("xanadu.txt"));
     outputStream = new PrintWriter(new FileWriter("characteroutput.txt"));
     String l;
     while ((l = inputStream.readLine()) != null) {
       outputStream.println(l);
     }
   } finally {
     if (inputStream != null) {
       inputStream.close();
     }
     if (outputStream != null) {
       outputStream.close();
     }
   }
 }

}

 </source>
   
  
 
  

List of lines in a file with BufferedReader

   <source lang="java">
 

/*

* Copyright (c) 1995 - 2008 Sun Microsystems, Inc.  All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
*   - Redistributions of source code must retain the above copyright
*     notice, this list of conditions and the following disclaimer.
*
*   - Redistributions in binary form must reproduce the above copyright
*     notice, this list of conditions and the following disclaimer in the
*     documentation and/or other materials provided with the distribution.
*
*   - Neither the name of Sun Microsystems nor the names of its
*     contributors may be used to endorse or promote products derived
*     from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
* IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
* THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER OR
* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/

import java.io.BufferedReader; import java.io.File; import java.io.FileReader; import java.io.IOException; import java.util.ArrayList; import java.util.List; import java.util.Random; public class FileList {

 public static void main(String[] args) {
   final int assumedLineLength = 50;
   File file = new File(args[0]);
   List<String> fileList = new ArrayList<String>((int) (file.length() / assumedLineLength) * 2);
   BufferedReader reader = null;
   int lineCount = 0;
   try {
     reader = new BufferedReader(new FileReader(file));
     for (String line = reader.readLine(); line != null; line = reader.readLine()) {
       fileList.add(line);
       lineCount++;
     }
   } catch (IOException e) {
     System.err.format("Could not read %s: %s%n", file, e);
     System.exit(1);
   } finally {
     if (reader != null) {
       try {
         reader.close();
       } catch (IOException e) {
       }
     }
   }
   int repeats = Integer.parseInt(args[1]);
   Random random = new Random();
   for (int i = 0; i < repeats; i++) {
     System.out.format("%d: %s%n", i, fileList.get(random.nextInt(lineCount - 1)));
   }
 }

}

 </source>
   
  
 
  

Read a text file

   <source lang="java">
 

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

 public static void main(String[] args) throws Exception {
   File file = new File("test.txt");
   StringBuffer contents = new StringBuffer();
   BufferedReader reader = null;
   reader = new BufferedReader(new FileReader(file));
   String text = null;
   // repeat until all lines is read
   while ((text = reader.readLine()) != null) {
     contents.append(text).append(System.getProperty("line.separator"));
   }
   reader.close();
   System.out.println(contents.toString());
 }

}

 </source>
   
  
 
  

Read content of a file

   <source lang="java">
 

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

 public static void main(String[] argv) {
   readTextFile(new File("c:\\a.txt"));
 }
 public static String readTextFile(File filename) {
   try {
     BufferedReader br = new BufferedReader(new FileReader(filename));
     StringBuilder sb = new StringBuilder();
     String line = br.readLine();
     while (line != null) {
       sb.append(line + "\n");
       line = br.readLine();
     }
     br.close();
     return sb.toString();
   } catch (Exception e) {
     e.printStackTrace();
     System.err.println(filename);
     System.err.println(e);
     return "";
   }
 }

}

 </source>
   
  
 
  

Read each line in a comma separated file into an array

   <source lang="java">
 

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

 public static void main(String[] args) throws Exception {
   BufferedReader br = new BufferedReader(new FileReader("thefile.csv"));
   String line = null;
   while ((line = br.readLine()) != null) {
     String[] values = line.split(",");
     for (String str : values) {
       System.out.println(str);
     }
   }
   br.close();
 }

}

 </source>
   
  
 
  

Read from a file using a BufferedReader

   <source lang="java">
 

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

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

}

 </source>
   
  
 
  

Reading Text from a File

   <source lang="java">
 

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

 public static void main(String[] argv) throws Exception {
   BufferedReader in = new BufferedReader(new FileReader("infilename"));
   String str;
   while ((str = in.readLine()) != null) {
     System.out.println(str);
   }
   in.close();
 }

}

 </source>
   
  
 
  

Read lines of text from a file with the BufferedReader class

   <source lang="java">
 

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

 public static void main(String[] args) throws Exception {
   BufferedReader br = new BufferedReader(new FileReader("filename.txt"));
   String line = null;
   while ((line = br.readLine()) != null) {
     System.out.println(line);
   }
   br.close();
 }

}

 </source>
   
  
 
  

ReadLines: read file to list of strings

   <source lang="java">

import java.io.BufferedReader; import java.io.File; import java.io.FileReader; import java.util.ArrayList; import java.util.List; public class Utils {

 public static List<String> readLines(File file) throws Exception {
     if (!file.exists()) {
         return new ArrayList<String>();
     }
     BufferedReader reader = new BufferedReader(new FileReader(file));
     List<String> results = new ArrayList<String>();
     String line = reader.readLine();
     while (line != null) {
         results.add(line);
         line = reader.readLine();
     }
     return results;
 }

}

 </source>
   
  
 
  

Tab filter: Convert tab to space characters

   <source lang="java">
 

import java.io.BufferedReader; import java.io.BufferedWriter; import java.io.FileReader; import java.io.FileWriter; class TabFilter {

 public static void main(String args[]) throws Exception {
   FileReader fr = new FileReader(args[0]);
   BufferedReader br = new BufferedReader(fr);
   FileWriter fw = new FileWriter(args[1]);
   BufferedWriter bw = new BufferedWriter(fw);
   // Convert tab to space characters
   String s;
   while ((s = br.readLine()) != null) {
     for (int i = 0; i < s.length(); i++) {
       char c = s.charAt(i);
       if (c == "\t")
         c = " ";
       bw.write(c);
     }
   }
   bw.flush();
   fr.close();
   fw.close();
 }

}

 </source>
   
  
 
  

Use BufferedReader to Read and process lines from console

   <source lang="java">
 

import java.io.BufferedReader; import java.io.InputStreamReader; class ReverseConsoleInput {

 public static void main(String args[]) throws Exception {
   InputStreamReader isr = new InputStreamReader(System.in);
   BufferedReader br = new BufferedReader(isr);
   // Read and process lines from console
   String s;
   while ((s = br.readLine()) != null) {
     StringBuffer sb = new StringBuffer(s);
     sb.reverse();
     System.out.println(sb);
   }
   isr.close();
 }

}

 </source>
   
  
 
  

Use BufferedReader to read line by line

   <source lang="java">
 

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

 public static void main(String args[]) throws Exception {
   File file = new File(".");
   if (file.isDirectory()) {
     String[] files = file.list();
     for (int i = 0; i < files.length; i++)
       System.out.println(files[i]);
   } else {
     FileReader fr = new FileReader(file);
     BufferedReader in = new BufferedReader(fr);
     String line;
     while ((line = in.readLine()) != null)
       System.out.println(line);
   }
 }

}

 </source>
   
  
 
  

Using BufferedReader to read input number from user

   <source lang="java">
 

import java.io.BufferedReader; import java.io.InputStreamReader; public class Main {

 public static void main(String[] args) throws Exception {
   BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
   String input = reader.readLine();
   double number = Double.parseDouble(input);
   System.out.println(input + ":" + Math.sqrt(number));
   reader.close();
 }

}

 </source>