Java Reference
In-Depth Information
File exists
Delete file
Copy
Source
does not
exist
F
IGURE
19.14
The program copies a file.
To copy the contents from a source file to a target file, it is appropriate to use an input
stream to read bytes from the source file and an output stream to send bytes to the target file,
regardless of the file's contents. The source file and the target file are specified from the
command line. Create an
InputFileStream
for the source file and an
OutputFileStream
for the target file. Use the
read()
method to read a byte from the input stream, and then use
the
write(b)
method to write the byte to the output stream. Use
BufferedInputStream
and
BufferedOutputStream
to improve the performance. Listing 19.4 gives the solution to
the problem.
L
ISTING
19.4
Copy.java
1
import
java.io.*;
2
3
public class
Copy {
4
/** Main method
5
@param args[0] for source file
6
@param args[1] for target file
7
*/
8
public static void
main(String[] args)
throws
IOException {
9
// Check command-line parameter usage
10
if
(args.length !=
2
) {
11 System.out.println(
12
"Usage: java Copy sourceFile targetFile"
);
13 System.exit(
1
);
14 }
15
16
check usage
// Check whether source file exists
File sourceFile =
new
File(args[
0
]);
17
18
if
(!sourceFile.exists()) {
19 System.out.println(
"Source file "
+ args[
0
]
20 +
" does not exist"
);
21 System.exit(
2
);
22 }
23
24
source file
// Check whether target file exists
File targetFile =
new
File(args[
1
]);
25
26
if
(targetFile.exists()) {
27 System.out.println(
"Target file "
+ args[
1
]
28 +
" already exists"
);
29 System.exit(
3
);
30 }
31
32
target file
// Create an input stream
BufferedInputStream input =
33
input stream
