Read all standard input into a Java byte array

Question

What\'s the simplest way in modern Java (using only the standard libraries) to read all of standard input until EOF into a byte array, preferably without having to prov

Answer 1

I'd use Guava and its ByteStreams.toByteArray method:

byte[] data = ByteStreams.toByteArray(System.in);

Without using any 3rd party libraries, I'd use a ByteArrayOutputStream and a temporary buffer:

ByteArrayOutputStream baos = new ByteArrayOutputStream();
byte[] buffer = new byte[32 * 1024];

int bytesRead;
while ((bytesRead = System.in.read(buffer)) > 0) {
    baos.write(buffer, 0, bytesRead);
}
byte[] bytes = baos.toByteArray();

... possibly encapsulating that in a method accepting an InputStream, which would then be basically equivalent to ByteStreams.toByteArray anyway...

Answer 2

If you're reading from a file, Files.readAllBytes is the way to do it.

Otherwise, I'd use a ByteBuffer:

ByteBuffer buf = ByteBuffer.allocate(1000000);
ReadableByteChannel channel = Channels.newChannel(System.in);
while (channel.read(buf) >= 0)
    ;
buf.flip();
byte[] bytes = Arrays.copyOf(buf.array(), buf.limit());