With this example we demonstrate how to copy files using FileChannels in Java. In particular we are going to read data from a specific file in the file system and write them to another file. In short what we do is the following :
- For the source file we create a FileChannel so as to be able to read data from. To do so you can create a FileInputStream object to encapsulate the target file. Then use the
getChannel()API method of the FileInputStream object to get the file channel - For the destination file we create a FileChannel so as to be able to write data to. To do so you can create a FileOutputStream object to encapsulate the target file. Then use the
getChannel()API method of the FileOutputStream object to get the file channel - To read a sequence of bytes from the source channel and write them to the destination channel all you have to do is use the
transferFrom(ReadableByteChannel, long, long)API method of the destination file’s FileChannel providing the source file’s FileChannel as the input attribute
as described in the code snippet below.
Do not forget to close the channel after you are done processing the file so as to release operating system resources.
package com.javacodegeeks.snippets.core;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.nio.channels.FileChannel;
public class CopyingBinaryFileWithFileChannel {
public static void main(String[] args) {
try {
// source file channel
// return the unique FileChannel object associated with this file input stream.
FileChannel srcChannel = new FileInputStream("src.dat").getChannel();
// destination file channel
// return the unique FileChannel object associated with this file output stream.
FileChannel dstChannel = new FileOutputStream("dst.dat").getChannel();
// transfer bytes into this channel's file from the given readable byte channel
dstChannel.transferFrom(srcChannel, 0, srcChannel.size());
// close channels
srcChannel.close();
dstChannel.close();
}
catch (IOException e) {
System.out.println("I/O Error: " + e.getMessage());
}
}
}
This was an example of how to copy files using FileChannel in Java.
