Java IO.pdf - Nguyen Dang Binh

12.3.4 Manipulating Files
Java I/O
The File class has methods to create, move, rename, and delete files. A method to copy files
is a noticeable omission.
12.3.4.1 Creating files
Java 1.1 provides no method to create a new file. Opening a file output stream to the file you
want to create, then immediately closing it, has the same effect. For example, the following
method creates a file if, and only if, it doesn't already exist. Otherwise, it throws an
IOException:
public static void createFileSafely(File f) throws IOException {
}
if (f.exists()) {
throw new IOException(f.getName() + " already exists.");
}
FileOutputStream fout = new FileOutputStream(f);
fout.close();
Java 2 adds the createNewFile() method:
public boolean createNewFile() throws IOException // Java 2
This method checks to see whether the file exists and creates the file if it doesn't already exist.
It returns true if the file was created and false if it wasn't created, either because it couldn't
be created or because the file already existed. For example:
File f = new File("output.dat");
boolean success = f.createNewFile();
if (success) {
//...
}
else { //...
This method throws an IOException if an I/O error occurs. It throws a security exception if
the security manager vetoes the creation of the file.
12.3.4.2 Moving and renaming files
The renameTo() method changes the name of a file:
public boolean renameTo(File destination)
For example, to change the name of the file src.txt in the current working directory to dst.txt,
you would write:
File src = new File("src.txt");
File dst = new File("dst.txt");
src.renameTo(dst);
As well as renaming the source file, renameTo()moves the source file from its original
directory to the directory specified by the destination argument if the destination file is in a
291