Yes; that is what the example program did.
The data are written as a stream of bytes. There are no gaps or markers that say where one value ends and another begins. The example program did this:
dataOut.writeInt( 0 ); dataOut.writeDouble( 12.45 );
An examination of the file shows the 12 bytes. Remember that dumps such as this print characters to show the pattern in one byte.
The six zeros at the beginning of the line mean the
the first byte shown is byte zero of the file.
The "f's" the end of the line show that some bytes
of the double
could also be interpreted
as characters.
Is it possible to tell just by looking at the bytes in a file what types the data are?