Answer / Explanation:
(1) We should first understand that the input filename are passed in as the first command arguments at command line, respectively.
To do this, we import the data file:
So we have,
import java.io.*;
/**
* Makes a copy of a file. The original file and the name of the
* copy must be given as command-line arguments. In addition, the
* first command-line argument can be "-f"; if present, the program
* will overwrite an existing file; if not, the program will report
* an error and end if the output file already exists. The number
* of bytes that are copied is reported.
*/
public class CopyFile {
public static void main(String[] args) {
String sourceName; // Name of the source file,
// as specified on the command line.
String copyName; // Name of the copy,
// as specified on the command line.
InputStream source; // Stream for reading from the source file.
OutputStream copy; // Stream for writing the copy.
boolean force; // This is set to true if the "-f" option
// is specified on the command line.
int byteCount; // Number of bytes copied from the source file.
/* Get file names from the command line and check for the
presence of the -f option.
(2) If the command line is not one
of the two possible legal forms, print an error message and
end this program. */
if (args.length == 3 && args[0].equalsIgnoreCase("-f")) {
sourceName = args[1];
copyName = args[2];
force = true;
}
else if (args.length == 2) {
sourceName = args[0];
copyName = args[1];
force = false;
}
else {
System.out.println(
"Usage: java CopyFile <source-file> <copy-name>");
System.out.println(
" or java CopyFile -f <source-file> <copy-name>");
return;
}
/* Create the input stream. If an error occurs, end the program. */
try {
source = new FileInputStream(sourceName);
}
catch (FileNotFoundException e) {
System.out.println("Can't find file \"" + sourceName + "\".");
return;
}
/* If the output file already exists and the -f option was not
specified, print an error message and end the program. */
File file = new File(copyName);
if (file.exists() && force == false) {
System.out.println(
"Output file exists. Use the -f option to replace it.");
return;
}
/* Create the output stream. If an error occurs, end the program. */
try {
copy = new FileOutputStream(copyName);
}
catch (IOException e) {
System.out.println("Can't open output file \"" + copyName + "\".");
return;
}
(3) /* Copy one byte at a time from the input stream to the output
stream, ending when the read() method returns -1 (which is
the signal that the end of the stream has been reached). If any
error occurs, print an error message. Also print a message if
the file has been copied successfully. */
byteCount = 0;
try {
while (true) {
int data = source.read();
if (data < 0)
break;
copy.write(data);
byteCount++;
}
source.close();
copy.close();
System.out.println("Successfully copied " + byteCount + " bytes.");
}
catch (Exception e) {
System.out.println("Error occurred while copying. "
+ byteCount + " bytes copied.");
System.out.println("Error: " + e);
}
} // end main()
} // end class CopyFile
