Java — Files

File handling is an important part of any application.

Java has several methods for creating, reading, updating, and deleting files.

Java File Handling

The File class from the java.io package, allows us to work with files.

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To use the File class, create an object of the class, and specify the filename or directory name:

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

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

Note: If you don’t know what a package is, read my Java Packages blog.

The File class has many useful methods for creating and getting information about files. Some common methods are shown below:

A table that shows common useful methods in Files (Java)

Create a File

To create a file in Java, you can use the createNewFile() method. 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):

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 should be:

File created: filename.txt

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

import java.io.File; 
import java.io.IOException;
  
public class CreateFileDir {  
  public static void main(String[] args) {  
    try {  
      File myObj = new File("C:\\Users\\MyName\\filename.txt"); //Directory
      if (myObj.createNewFile()) {  
        System.out.println("File created: " + myObj.getName());  
        System.out.println("Absolute path: " + myObj.getAbsolutePath());  
      } 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
Absolute path: C:\Users\MyName\filename.txt

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:

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("Java wrote something in this file!");
      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.

Read a File

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

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();
    }
  }
}

The output will be:

Java wrote something in this file!

Get File Information

To get more information about a file, use any of the File methods:

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

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:\Users\MyName\filename.txt
Writeable: true
Readable: true
File size in bytes: 0

Note: There are many available classes in the Java API that can be used to read and write files in Java: FileReader, BufferedReader, Files, Scanner, FileInputStream, FileWriter, BufferedWriter, FileOutputStream, etc. Which one to use depends on the Java version you're working with and whether you need to read bytes or characters, and the size of the file/lines etc.

Delete a File

To delete a file in Java, use the delete() method:

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

public class DeleteFile {
  public static void main(String[] args) { 
    File myObj = new File("filename.txt"); 
    if (myObj.delete()) { 
      System.out.println("Deleted the file: " + myObj.getName());
    } else {
      System.out.println("Failed to delete the file.");
    } 
  } 
}

The output will be:

Deleted the file: filename.txt

Delete a Folder

You can also delete a folder. However, it must be empty:

import java.io.File; 

public class DeleteFolder {
  public static void main(String[] args) { 
    File myObj = new File("C:\\Users\\MyName\\Test"); 
    if (myObj.delete()) { 
      System.out.println("Deleted the folder: " + myObj.getName());
    } else {
      System.out.println("Failed to delete the folder.");
    } 
  } 
}

The output will be:

Deleted the folder: Test