Question

Below is the code that I have written. I want to do the simple thing, storing binary file data into byteBuffer.

File file = new File(fileName);
try {
    ReadableByteChannel channel = new FileInputStream(fileName).getChannel();
    ByteBuffer buf = ByteBuffer.allocateDirect(file.length());

    // How can use buf.read to get all the contents?

} catch (Exception e){

}

I was wondering

1. how can I use read to get all data from channel and store it in ByteBuffer
2. if there is more elegant way to allocate ByteBuffer, other than using File object to get the length of the file

Answer 1

From the ReadableByteChannel Javadocs

read(ByteBuffer dst)

An attempt is made to read up to r bytes from the channel, where r is the number of bytes remaining in the buffer, that is, dst.remaining(), at the moment this method is invoked.

So … channel.read(buf);

As for your second question, if you want to read the entire contents of the file into memory at once that seems like a reasonable approach.