Java Programming Tutorial – 81 – Reading from Files

Bucky made a file named chinese and was coughing in this tutorial. He tried to warn us all but we didn't listen.

i did the same like you but instead of showing me the text on console it says null in a continuous way. How can i resolve this issue? Please help

if your code doesn't work when you used
String a = x.next();

String b = x.next();

String c = x.next();
it means that you have not given 3 kinds of data in one line or you have more. example 120 bucky roberts. a=120 b=bucky c=roberts.

Hey I know this is probably a long shot considering how old the video is but if you could respond that would be awesome. I was wondering how you split up that string and give them variables. Thank you so much if you are seeing this.

Dude you totally saved me!! THANK YOU!!!!

THANK YOU <3

3:53 what if i have a custom public class 'Item' and instead of doing what's shown in the video, I wanna instantiate into 'Item' object? Hope this question makes sense

We miss you! <3

amazing vid, cheers man

Can you use Print Writer in the same place? And stor it into that text file?

are you creating new classes every time that you make a video?

import java.io.File;  // Import the File class

File myObj = new File("filename.txt"); // Specify the filename

The File class has many useful methods for creating and getting information about files. For example:

MethodTypeDescriptioncanRead()BooleanTests whether the file is readable or notcanWrite()BooleanTests whether the file is writable or notcreateNewFile()BooleanCreates an empty filedelete()BooleanDeletes a fileexists()BooleanTests whether the file existsgetName()StringReturns the name of the filegetAbsolutePath()StringReturns the absolute pathname of the filelength()LongReturns the size of the file in byteslist()String[]Returns an array of the files in the directorymkdir()BooleanCreates a directory

If you don't know what a package is, read our Java Packages Tutorial.

Create a File

Use the createNewFile() method to create a file. This method returns a boolean value: true if the file was successfully created, and false if the file already exists. Note that the method is enclosed in a try…catch block. This is necessary because it throws an IOException if an error occurs (if the file cannot be created for some reason):

Example

import java.io.File;  // Import the File class
import java.io.IOException;  // Import the IOException class to handle errors

public class CreateFile {
  public static void main(String[] args) {
    try {
      File myObj = new File("filename.txt");
      if (myObj.createNewFile()) {
        System.out.println("File created: " + myObj.getName());
      } else {
        System.out.println("File already exists.");
      }
    } catch (IOException e) {
      System.out.println("An error occurred.");
      e.printStackTrace();
    }
  }
}

The output will be:

File created: filename.txt

Run example »

To create a file in a specific directory (requires permission), specify the path of the file and use double backslashes to escape the "" character (for Windows). On Mac and Linux you can just write the path, like: /Users/name/filename.txt

Example

File myObj = new File("C:\Users\MyName\filename.txt");

Run example »

Get File Information

Now that we have created a file, we can use other File methods to get information about that file:

Example

import java.io.File;

public class GetFileInfo {
  public static void main(String[] args) {
    File myObj = new File("filename.txt");
    if (myObj.exists()) {
      System.out.println("File name: " + myObj.getName());
      System.out.println("Absolute path: " + myObj.getAbsolutePath());
      System.out.println("Writeable: " + myObj.canWrite());
      System.out.println("Readable " + myObj.canRead());
      System.out.println("File size in bytes " + myObj.length());
    } else {
      System.out.println("The file does not exist.");
    }
  }
}

The output will be:

File name: filename.txt
Absolute path: C:UsersMyNamefilename.txt
Writeable: true
Readable: true
File size in bytes: 0

Run example »

Write To a File

In the following example, we use the FileWriter class together with its write() method to write some text to the file we created in the example above. Note that when you are done writing to the file, you should close it with the close() method:

Example

import java.io.FileWriter;   // Import the FileWriter class
import java.io.IOException;  // Import the IOException class to handle errors

public class WriteToFile {
  public static void main(String[] args) {
    try {
      FileWriter myWriter = new FileWriter("filename.txt");
      myWriter.write("Files in Java might be tricky, but it is fun enough!");
      myWriter.close();
      System.out.println("Successfully wrote to the file.");
    } catch (IOException e) {
      System.out.println("An error occurred.");
      e.printStackTrace();
    }
  }
}

The output will be:

Successfully wrote to the file.

Run example »

Read a File

In the following example, we use the Scanner class to read the contents of the text file we created in the example above:

Example

import java.io.File;  // Import the File class
import java.io.FileNotFoundException;  // Import this class to handle errors
import java.util.Scanner; // Import the Scanner class to read text files

public class ReadFile {
  public static void main(String[] args) {
    try {
      File myObj = new File("filename.txt");
      Scanner myReader = new Scanner(myObj);
      while (myReader.hasNextLine()) {
        String data = myReader.nextLine();
        System.out.println(data);
      }
      myReader.close();
    } catch (FileNotFoundException e) {
      System.out.println("An error occurred.");
      e.printStackTrace();
    }
  }
}