Reading Files - Beginning Java - page 523

• AsynchronousCloseException is thrown if either channel is closed by another thread while the
operation is in progress.
• ClosedByInterruptException is thrown if another thread interrupts the current thread while the
operation is in progress.
• IOException is thrown if some other I/O error occurs.
The value of these methods lies in the potential for using the I/O capabilities of the underlying operating
system directly. Where this is possible, the operation is likely to be much faster than copying from one file
to another in a loop using the read() and write() methods you have seen.
A file copy program is an obvious candidate for trying out these methods.

TRY IT OUT: Direct Data Transfer between Channels
This example is a program that copies the file that is specified by a command-line argument. You copy
the file to a backup file that you create in the same directory as the original. You create the name of the
new file by appending "_backup" to the original filename as many times as necessary to form a unique
filename. That operation is a good candidate for writing a helper method:

// Method to create a unique backup Path object under MS Windows
public static Path createBackupFilePath(Path file) {
Path parent = file.getParent();
String name = file.getFileName().toString(); // Get the

file name
int period = name.indexOf('.'); // Find the extension

separator
if(period == -1) { // If there isn't one

period = name.length(); // set it to the end of

the string
}
String nameAdd = "_backup"; // String to be appended

// Create a Path object that is a unique
Path backup = parent.resolve(
name.substring(0,period) + nameAdd +
name.substring(period));
while(Files.exists(backup)) { // If the path already

exists...
name = backup.getFileName().toString(); // Get the current
file name
backup = parent.resolve(name.substring(0,period) + // add

_backup

nameAdd + name.substring(period));
period += nameAdd.length(); // Increment separator

index
}
return backup;