Create a File object in memory from a string in Java

Question

I have a function that accepts File as an argument. I don\'t want to create/write a new File (I don\'t have write access to filesystem) in order to pass my string data to th

Answer 1

A File object in Java is a representation of a path to a directory or file, not the file itself. You don't need to have write access to the filesystem to create a File object, you only need it if you intend to actually write to the file (using a FileOutputStream for example)

Answer 2

No; instances of class File represent a path in a filesystem. Therefore, you can use that function only with a file. But perhaps there is an overload that takes an InputStream instead?

Answer 3

Usually when a method accepts a file, there's another method nearby that accepts a stream. If this isn't the case, the API is badly coded. Otherwise, you can use temporary files, where permission is usually granted in many cases. If it's applet, you can request write permission.

An example:

try {
    // Create temp file.
    File temp = File.createTempFile("pattern", ".suffix");

    // Delete temp file when program exits.
    temp.deleteOnExit();

    // Write to temp file
    BufferedWriter out = new BufferedWriter(new FileWriter(temp));
    out.write("aString");
    out.close();
} catch (IOException e) {
}

Answer 4

FileReader r = new FileReader(file);

Use a file reader load the file and then write its contents to a string buffer.

example

The link above shows you an example of how to accomplish this. As other post to this answer say to load a file into memory you do not need write access as long as you do not plan on making changes to the actual file.

Answer 5

The File class represents the "idea" of a file, not an actual handle to use for I/O. This is why the File class has a .exists() method, to tell you if the file exists or not. (How can you have a File object that doesn't exist?)

By contrast, constructing a new FileInputStream(new File("/my/file")) gives you an actual stream to read bytes from.