File Handling

File Handling:

           sample.txt

-----------------------

               line-1

               line-2

               line-3

               line-4

----------------------

Basic operations:

               1.read note pad file data through code

               2.      write line1

                              write line 2

                              write line 3

               3.append the data

// To read note pad .txt file - we have some predefined class and predefined methods

      write

FileReader

Bufferedreader

                 readLine()

ex: read Line from notepad file?

 

package FileHanldingBasics;

import java.io.BufferedReader;

import java.io.File;

import java.io.FileNotFoundException;

import java.io.FileReader;

import java.io.IOException;

public class ReadingNotePadFile {

               public static void main(String[] args) throws IOException {

                              // Create .txt/  note pad file and enter some lines of data

                              // FileReader, BufferedReader - classes

                              // create obj for 'FileReader' class

                              //                                         

                              File f = new File("C:\\brahma\\Practise\\SelniumPractiseNew\\March52024MyWorkspace\\SampleJavaProject2\\src\\FileHanldingBasics\\TestData.txt");

                              FileReader fr = new FileReader(f);

                              //Unhandled exception type FileNotFoundException  - checked Exception

                              // create obj  for 'BufferedReader' and pass 'fr'

                              BufferedReader br = new BufferedReader(fr);

                              // read line -1

                              String Line1 = br.readLine();

                              // Unhandled exception type IOException -- checked exception -or Compile Time exception

                              // compiler identifies checked exceptions

                              System.out.println("Line1="+ Line1);

                              // read line -2

                              String line2 = br.readLine();

                              System.out.println("line2="+line2);

                              // read line -3

                              String line3 = br.readLine();

                              System.out.println("line3="+line3);

                              // Read line -4 that is not there in notepad

                              //  null - nothing to read from notepad file

                              String line4 = br.readLine();

                              //                  null

                              System.out.println("line4="+ line4);

                                            

               }

}

HW create new notepad sample2.txt and write 5 lines and read 5 lines ?

//FAQ  Read all data from note pad (or) text file?

package FileHanldingBasics;

import java.io.BufferedReader;

import java.io.File;

import java.io.FileNotFoundException;

import java.io.FileReader;

import java.io.IOException;

public class ReadingAllDataFromNotePadFile {

               public static void main(String[] args) throws IOException {

//                           System.out.println("hi");

                              // To read note pad .txt file - we have some predefined class and predefined methods

                              // Create  note pad file and enter some lines of data

                              // create obj for FileReader class

                              //                                                         File f = new File("C:\\brahma\\Practise\\SelniumPractiseNew\\NovSeleniumBatchWorkSpace\\JavaNovBatchProject\\src\\FileHandlingBasics\\TestData.txt");

                              //                                                         FileReader

                              //                                                         BufferedReader

                              File f = new File("C:\\brahma\\Practise\\SelniumPractiseNew\\March52024MyWorkspace\\SampleJavaProject2\\src\\FileHanldingBasics\\TestData.txt");

                              FileReader fr = new FileReader(f);

                              BufferedReader br = new BufferedReader(fr);

                              // read all lines from notepad

//                           br.readLine();

//                           br.readLine();

//                           br.readLine();

                              while(br.readLine()!=null)

                              {

                                             String data = br.readLine();

                                             System.out.println(data);

                              }

               }

}

o/p:

How are you?

null

-------------------------------

package FileHanldingBasics;

import java.io.BufferedReader;

import java.io.File;

import java.io.FileNotFoundException;

import java.io.FileReader;

import java.io.IOException;

public class ReadingAllDataFromNotePadFile {

               public static void main(String[] args) throws IOException {

//                           System.out.println("hi");

                              // To read note pad .txt file - we have some predefined class and predefined methods

                              // Create  note pad file and enter some lines of data

                              // create obj for FileReader class

                              //                                                         File f = new File("C:\\brahma\\Practise\\SelniumPractiseNew\\NovSeleniumBatchWorkSpace\\JavaNovBatchProject\\src\\FileHandlingBasics\\TestData.txt");

                              //                                                         FileReader

                              //                                                         BufferedReader

                              File f = new File("C:\\brahma\\Practise\\SelniumPractiseNew\\March52024MyWorkspace\\SampleJavaProject2\\src\\FileHanldingBasics\\TestData.txt");

                              FileReader fr = new FileReader(f);

                              BufferedReader br = new BufferedReader(fr);

                              // read all lines from notepad

//                           br.readLine();

//                           br.readLine();

//                           br.readLine();

                              String x = "";

                             

                              while((x=br.readLine())!=null)

                              {

//                                          String data = br.readLine();

                                             System.out.println(x);

                              }

               }

}

o/p:

This is Ram.

How are you?

I am fine.What about you?

 

Write notepad file (or) text file:

package FileHanldingBasics;

import java.io.BufferedWriter;

import java.io.File;

import java.io.FileWriter;

import java.io.IOException;

public class WriteDatatoNotePadFile {

               public static void main(String[] args) throws IOException {

                              // Read data -->   FileReader, BufferedReader classes

                              // Write data -->  FileWriter,  BufferedWriter classes

                             

                             

//           

                              File f  = new File("C:\\brahma\\Practise\\SelniumPractiseNew\\March52024MyWorkspace\\SampleJavaProject2\\src\\FileHanldingBasics\\Sample.txt");

                              FileWriter fw = new FileWriter(f);                            

                              // Unhandled exception type IOException

                              BufferedWriter bw = new BufferedWriter(fw);

                             

                              //  To write data into notepad - we have some method --

                              // write line-1

                              bw.write("This is line-1");

                              // write line-2

                              bw.write("This is line-2");

                              // write line-3

                              bw.write("This is line-3");

                             

                              // if we dont use flush , data will not be written in notepad file

                              bw.flush();

                             

                              System.out.println("ends");                        

               }

}

o/p:

open Sample.txt file, we can see belwo o/p

This is line-1This is line-2This is line-3

Write data into new line()

Line-1

Line-2

Line-3

package FileHanldingBasics;

import java.io.BufferedWriter;

import java.io.File;

import java.io.FileWriter;

import java.io.IOException;

public class WriteDatatoNotePadFile {

               public static void main(String[] args) throws IOException {

                              // Read data -->   FileReader, BufferedReader classes

                              // Write data -->  FileWriter,  BufferedWriter classes

                             

                             

//           

                              File f  = new File("C:\\brahma\\Practise\\SelniumPractiseNew\\March52024MyWorkspace\\SampleJavaProject2\\src\\FileHanldingBasics\\Sample.txt");

                              FileWriter fw = new FileWriter(f);                            

                              // Unhandled exception type IOException

                              BufferedWriter bw = new BufferedWriter(fw);

                             

                              //  To write data into notepad - we have some method --

                              // write data into new lines

                             

                              // write line-1

                              bw.write("This is line-1");

                              bw.newLine();

                              // write line-2

                              bw.write("This is line-2");

                              bw.newLine();

                              // write line-3

                              bw.write("This is line-3");

                              bw.newLine();

                             

                              // if we dont use flush , data will not be written in notepad file

                              bw.flush();

                             

                              System.out.println("ends");                        

               }

}

o/p:

open note pad :

This is line-1

This is line-2

This is line-3

or

write data into new line using '\n':

package FileHanldingBasics;

import java.io.BufferedWriter;

import java.io.File;

import java.io.FileWriter;

import java.io.IOException;

public class WriteDatatoNotePadFile {

               public static void main(String[] args) throws IOException {

                              // Read data -->   FileReader, BufferedReader classes

                              // Write data -->  FileWriter,  BufferedWriter classes

                             

                             

//           

                              File f  = new File("C:\\brahma\\Practise\\SelniumPractiseNew\\March52024MyWorkspace\\SampleJavaProject2\\src\\FileHanldingBasics\\Sample.txt");

                              FileWriter fw = new FileWriter(f);                            

                              // Unhandled exception type IOException

                              BufferedWriter bw = new BufferedWriter(fw);

                             

                              //  To write data into notepad - we have some method --

                              // write data into new lines

                              //  To write data into new line using \n

                                             // \n represents new line char

                                            

                              // write line-1

                              bw.write("This is line-1\n");

                             

                              // write line-2

                              bw.write("This is line-2\n");

                             

                              // write line-3

                              bw.write("This is line-3");

                             

                             

                              // if we dont use flush , data will not be written in notepad file

                              bw.flush();

                             

                              System.out.println("ends");                        

               }

}

o/p:

This is line-1

This is line-2

This is line-3

Write the o/p for below code:

package FileHanldingBasics;

import java.io.BufferedWriter;

import java.io.File;

import java.io.FileWriter;

import java.io.IOException;

public class WriteDatatoNotePadFile2 {

               public static void main(String[] args) throws IOException {

                              // Read data --   Filereader, BufferedReadrer classes

                              // Write data -  FileWriter , BufferedWriter

                              File f = new File("C:\\brahma\\Practise\\SelniumPractiseNew\\March52024MyWorkspace\\SampleJavaProject2\\src\\FileHanldingBasics\\Sample.txt");

                              FileWriter  fw =  new FileWriter(f);

                              // Unhandled exception type IOException

                              BufferedWriter bw=  new BufferedWriter(fw);

                              //  To write data into notepad - we ahve some method

                              bw.write("Line-1\n code\n");// \n represents new line char

                              bw.write("Line-2 code\n");

                              bw.write("Line-3 code");

                              // \t  tab = enter 5 spaces

                              //   Ram               is            good      boy.

                              bw.write("\nRam is good boy\n");

                              bw.write("Ram\t is\t good\t boy");

                              bw.flush();// if we don't call flush() , data will not  be written in notepad file

                              System.out.println("ends");

               }

}

o/p:

Line-1

 code

Line-2 code

Line-3 code

Ram is good boy

Ram       is           good     boy

---------------------------------

Note:

               String s= "Ram \n sita\n lakshman";

                              System.out.print("s="+s);

o/p:

s=Ram

 sita

 lakshman

FAQ IP //HW  WAP to count no of lines  from notepad.

i/p:

  this is ram.

  How are you?.

  I am fine.What about you?

o/p:  lines cnt  = 3

HW Write a separate method  to Get given Lineno - data ?

i/p:

  this is ram.

  How are you?.

  I am fine. What about you?

  where are u staying.

  I am in marathahalli.

  getDataBasedOnGivenLineNo(1); o/p   this is ram.

  getDataBasedOnGivenLineNo(2); o/p:   How are you?.

 

 String  getDataBasedOnGivenLineNo(int lineNo)

{

              

}

Append data to existing File:

-----------------------------

    sample.txt

------------

line-1

line-2

line -3 appending

line -4 apending

// appending:  adding data to to end of file

                              //   existing data +  add some data to end of file

                             

package FileHanldingBasics;

import java.io.BufferedWriter;

import java.io.File;

import java.io.FileWriter;

import java.io.IOException;

public class appendDataToExistingFile {

               public static void main(String[] args) throws IOException {

                              // Read data --   Filereader, BufferedReadrer classes

                              // Write data -  FileWriter , BufferedWriter

                              File f  = new File("C:\\brahma\\Practise\\SelniumPractiseNew\\March52024MyWorkspace\\SampleJavaProject2\\src\\FileHanldingBasics\\DataAppend.txt");

//                           FileWriter fw =  new FileWriter(f);//  it always enter new data  -Overwrite existing data

//                                                         (or)

//                           FileWriter fw =  new FileWriter(f,false);//  it will not append data - overwrite existing data

                              // append                                                                                      // append

                              //    true -  append data  -  dont overwrite data in notepad

                              FileWriter fw = new FileWriter(f, true);

                              BufferedWriter bw = new BufferedWriter(fw);

                             

                              // appending Ram-1

                              bw.append("appending Ram-2");

                             

                              // append Sita-1

                              bw.append("append Sita-2");

                              // flush

                              bw.flush();

                              System.out.println("ends");

               }

}

o/p:

open file :

This is line -1

This is line-2.appending Ram-1append Sita-1appending Ram-2append Sita-2

Note: appending means adding data at the end only.