Java cp
A simple copy utility
On of the Remember Java visitors recently requested an example on how to
opy files in Java. And more specifically, how to copy
a section of one file into a new one. The following classes brings you
two very simple solutions, which you could develop further.
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The first example is over-simplified; it has no user input error checking,
no access checking and will overwrite any existing file. The only thing to
note, is the use of the buffered streams for input and output. This enables
efficent file operations without having to write extra code. In fact,
it boils the actual copy operation down to a single lined while loop.
BufferedInputStream in = new BufferedInputStream(new FileInputStream(src));
BufferedOutputStream out = new BufferedOutputStream(new FileOutputStream(dest));
int b;
while( (b = in.read()) != -1) {
out.write(b);
}
in.close();
out.close();
CopyFile.java
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The second example adds some user input and file access checks; it will
terminate if two file arguments are not supplied, but also if the source
argument is not an existing file or it can not be read. Finally, it will
stop if the destination file already exisits, which could of course be change
to depend on some user argument.
CopyFile.java
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The finaly example this week will do what was originally requested; copy
only a section of the source file to a new destination file. Two new arguments
are thus required: the offset at which to start reading, and the number of
bytes (or alternativly lines) to read. We'll make the example as simple as possible;
four arguments are required, two for source and destination files, and two for
start offset and length of sub-section:
java CopyFilePart <source> <destination> <start> <length>
CopyFilePart.java
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