Creating temporary files
Every once in a while we have to create a temporary file to store some information. We only want it to use in our application and it must have a unique name. Preferably we want to store the file in the system's temporary folder, so we don't have to do any housekeeping for storing the files.

Since JDK1.2 we can use the createTempFile() method in the File class. This method is a static method and returns a File object we can use to store information in. We don't have to worry about uniqueness of the name, because the Java VM will take care of that. And the file can be created in the system's temporary folder automatically.

The createTempFile() method has three parameters:

• prefix: The text to be used for the start of the temporary filename. The text cannot be empty, we must assign a value with a length greater than 0.
• suffix: The text at the end of the filename. Here we can set the extension of the filename by using a dot (.). The suffix may be an empty String opposed to the prefix.
• directory: Optionally we can use a different directory instead of the system's temporary directory.

Let's take a look at a small example, in which the createTempFile() method is used.

    File tempFile = null;
    try {
      tempFile = File.createTempFile("www.drbob42.com", ".tmp");
      System.out.print("Created temporary file with name ");
      System.out.println(tempFile.getAbsolutePath());
    } catch (IOException ex) {
      System.err.println("Cannot create temp file: " + ex.getMessage());
    } finally {
      if (tempFile != null) {
        tempFile.delete();
      }
    }

  Created temporary file with name C:\TEMP\www.drbob42.com56873.tmp