Writes to the output stream all the bytes in array b. If b is null, a NullPointerException is thrown. If b.length is zero, then no bytes are written. Otherwise, the byte b[0] is written first, then b[1], and so on; the last byte written is b[b.length-1].
writeBytes(String s) :
Writes a string to the output stream. For every character in the string s, taken in order, one byte is written to the output stream. If s isnull, a NullPointerException is thrown.