Where does Java File instance store?

Question

I have a question regarding to the Java File class. When I create a File instance, for example,

File aFile = new File(path);

Where does the instance aFile store in the computer? Or it stores in JVM? I mean is there a temp file stored in the local disk?

If I have an InputStream instance, and write it to a file by using OutputSteam, for example

  File aFile = new File("test.txt");

  OutputStream anOutputStream = new FileOutputStream(aFile);

  byte aBuffer[] = new byte[1024];

  while( ( iLength = anInputStream.read( aBuffer ) ) > 0)
  {
    anOutputStream.write( aBuffer, 0, iLength);
  }

Now where does the file test.txt store?

Thanks in advance!

Jon Skeet · Accepted Answer · 2011-08-22 15:00:22Z

6

A File object isn't a real file at all - it's really just a filename/location, and methods which hook into the file system to check whether or not the file really exists etc. There's no content directly associated with the File instance - it's not like it's a virtual in-memory file, for example. The instance itself is just an object in memory like any other object.

Creating a File instance on its own does nothing to the file system.

When you create a FileOutputStream, however, that does affect whatever file system you're writing to. The File instance is relatively irrelevant though - you'd get the same effect from:

OutputStream anOutputStream = new FileOutputStream("test.txt");

answered Aug 22, 2011 at 15:00

Jon Skeet

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Cygnusx1 · Accepted Answer · 2011-08-22 15:14:55Z

1

It will write the file where you specify it with path arguement.

In your case, it will write it in the directory where you run your java class.

If you specify /test/myproject/myfile.txt

it will go in /test/myproject/myfile.txt

edited Aug 22, 2011 at 15:14

answered Aug 22, 2011 at 15:01

Cygnusx1

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Reverend Gonzo · Accepted Answer · 2011-08-22 14:59:19Z

0

If you don't provide a path, it is in the current directory (ie: the directory where java.exe is executed from.) If you provide a full path, it is stored there.

Regardless, it is always stored in the filesystem, not in JVM memory.

answered Aug 22, 2011 at 14:59

Reverend Gonzo

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