Basic File Handling in Java - Part 2

In the previous article, we discussed about two basic file handling functions in Java including searching for an existing created file in the system and creating a file using java’s inbuilt function.

In this article we will cover up the other two file handling operations which includes reading from a file and writing to a file using java’s own methods. In this program we create a file by specifying a file name, open it at the same time and add records to it as per custom format. After writing to the file, it is good practice to close it.

import java.io.*;

import java.lang.*;

import java.util.*;

public class FileHandlingTrial {

       private Formatter file;

      

              public void openFile (){ //creating & opening a file

                    

                     try{

                           file= new Formatter("New Text Document.txt"); //will be created in default workspace folder else specify a path

                     }

                    

                     catch(Exception e){

                           System.out.println("Illegal file operation");

                                 

                           }

                     }

                    

                     public void addRecords(){// writes to the created file

                           file.format("%s %s %s", "99", "MCA", "IP University");

                    

                     }

                    

                     public void closeFile(){ //good practice to close the file after use

                           file.close();

                     }

      

}

class FileHandlingTrial1 {

      

       public static void main(String[] args){

             

         FileHandlingTrial asp = new FileHandlingTrial();

        

         asp.openFile();

         asp.addRecords();

         asp.closeFile();

             

       }

}

In this last program of file handling we will read the content added by the user.

Here also we create three methods in which first opens the file, second reads the content of the file and third one finally closes the file after reading the contents.

import java.io.*;

import java.util.*;

public class FileHandlingTrial {

private Scanner file;

public void openFile(){ // to open the file

      

       try{

              file = new Scanner(new File("new.txt"));

             

             

       }

      

       catch(Exception e){

             

              System.out.println("File not found");

       }

}

public void readFile(){ // to read data from the file

      

       while(file.hasNext()){

              String a=file.next();

              String b=file.next();

              String c=file.next();

              String d=file.next();

             

              System.out.printf("%s %s %s %s\n", a, b, c, d);

             

}

}

public void closeFile(){

file.close();

}

}

class FileHandlingTrial1 {

      

       public static void main(String[] args){

             

         FileHandlingTrial asp = new FileHandlingTrial();

        

         asp.openFile();

         asp.readFile();

         asp.closeFile();

             

       }

}

Screenshot // click to open a higher resolution version

Basic File Handling in Java – Part 1

Java provides File class in ‘java.io’ package for handling all basic and necessary file operations and methods used for file handling like reading the contents of a file, writing to a file, searching for a file, determining the path of the file stored on a disk, etc. File class contains number of methods for performing specific operations on a file, few of which are used in this article.

In this program, the user is checking for the existence of a particular file stored on system’s hard disk. File class of Java IO package has been used to provide access to methods like exists(), getName() which checks for the file and if found returns the message else gives user defined message.

import java.io.File; //file class for basic file operations

class FileHandlingTrial{

               

         public static void main(String[] args) {

                               

  File asp = new File("C:\\file\\info.txt"); // constructor takes the path of the file already existing on the system

                               

             if(asp.exists()) // built in method to test whether a specified file exists or not.

                                               

                        System.out.println(asp.getName() + "File Found"); // prints the message along with file name

                                               

                                        else

                        System.out.println("File Not Found");

                               

                }

}

In the previous program we checked for an already created file on the system. We can also create a file using the program with help of facilities provided by java.io package

import java.util.*;

class FileHandlingTrial{

               

                public static void main(String[] args) {

                               

                                final Formatter asp; //formatter print strings to file

                               

                                try{

                                      asp = new Formatter("c://file//trial.txt"); //provide path of file where it will be stored

                                               

                                                System.out.println("File Created");

                                }

                               

                                catch(Exception e){

                                               

                             System.out.println("Error"); // for possible mistyping of wrong or illegal folder location like specifying a drive which does not exist on system.

                                }

                                               

                }

}

In the next article which will be part 2 of file handling, reading from a file and writing to a file will be discussed. Thanks folks for reading. 

Screenshot // click to open a higher resolution version