Java Create Temporary File

Creating a temporary file in Java can be required in many scenarios, but mostly it will happen during unit tests where we don’t want to store the output of the intermediate operations. As soon as the test is finished, we do not need these temp files and we can delete them.

While unit testing using Junit, you can use TemporaryFolder as well. The TemporaryFolder rule allows creation of files and folders that are guaranteed to be deleted when the test method finishes (whether it passes or fails).

1. File.createTempFile()

The createTempFile() is an overloaded method. Both methods create a new empty temporary file. If the target directory argument is not specified, file is created in the the default temporary-file directory specified by the system property java.io.tmpdir.

Both methods will create the file only if there is not file with same name and location that exist before the method is called.

If we want the file to be deleted automatically, use the deleteOnExit() method.

File createTempFile(String prefix, String suffix) throws IOException
File createTempFile(String prefix, String suffix, File directory) throws IOException

Example 1: Creating a temporary file with specific name

public class TemporaryFileExample
{
   public static void main(String[] args)
   {
      File temp;
      try
      {
         temp = File.createTempFile("myTempFile", ".txt");
		 
         System.out.println("Temp file created : " + temp.getAbsolutePath());
      } catch (IOException e)
      {
         e.printStackTrace();
      }
   }
}

Program Output:

Temp file created : C:\Users\admin\AppData\Local\Temp\myTempFile3492283537103788196.txt

2. Files.createTempFile() – Java NIO

This createTempFile() is also an overloaded method. Both methods create a new empty temporary file.

If we want the file to be deleted automatically, open the file with DELETE_ON_CLOSE option so that the file is deleted when the appropriate close() method is invoked.

Path createTempFile(String prefix, String suffix, FileAttribute<?>... attrs)
Path createTempFile(Path dir, String prefix, String suffix, FileAttribute<?>... attrs)

Example 2: Creating a temporary file in temp folder

In the given example, the created temporary file will be deleted when the program exits.

public class TemporaryFileExample
{
   public static void main(String[] args)
   {
      try
      {
         final Path path = Files.createTempFile("myTempFile", ".txt");
         System.out.println("Temp file : " + path);
         
         //Delete file on exit
         path.toFile().deleteOnExit();
         
      } catch (IOException e)
      {
         e.printStackTrace();
      }
   }
}

Happy Learning !!