how to delete the content of text file without deleting itself

Question

I want to copy the content of file \'A\' to file \'B\'. after the copying is done I want to clear the content of file \'A\' and want to write on it from its beginning. I can

Answer 1

One liner to make truncate operation:

FileChannel.open(Paths.get("/home/user/file/to/truncate"), StandardOpenOption.WRITE).truncate(0).close();

More information available at Java Documentation: https://docs.oracle.com/javase/7/docs/api/java/nio/channels/FileChannel.html