String#getBytes() or much better String#getBytes(Charset charset)/String#getBytes(String charsetname) returns a "binary" representation as a byte. You want a specific representation of the bytes when printed to the console? Arrays.toString delivers one, but obviously not the one you want.
You need to iterate over the array of byte and print every byte as a binary representation. You want something like "10010110", I guess? Integer.toBinaryString(int) would do.
But keep in mind that this will not show you the bytes in the string but the bytes of a specific representation. If you want ASCII you need to supply the Charset to the getBytes method. If you don't than your platforms default charset will be used which will in most cases not be ASCII - but if it is a superset like ISO-8859 this may go unnoticed.
Sure, if you get the file as byte then you just don't need the detour with String#getBytes(String). If at one point in your data flow you get the file contents as string you have to carefully look at every place where you convert the data. Never forget an explicit charset then.
I do want the "10010110" representation.
Just to be sure - we are talking about the string representation here? "1"s and "0"s taken from a charset, the result being a string. I ask just because I can hardly think of a situation where I would need a string representation of the bits of a file content...