java - IndexOutOfBoundsException when use MappedByteBuffer -

i thinking of using mappedbytebuffer store/load data file. let's assume have field of type long , field b of string looks below when serialized: a(long) | b(string)

now want write , read it. here piece of sample code:

randomaccessfile file = new randomaccessfile(datapath.tostring(), "rw");     mappedbytebuffer mbb = file.getchannel().map(filechannel.mapmode             .read_write, 0, 256);     long num = 500;     mbb.putlong(0, num); // (1) first write long value @ beginning     string str = "hello world!";     byte[] input = str.getbytes();     //then write string     mbb.put(input, 8, input.length); // (2) indexoutofboundsexception 

so later can retrieve long calling mbb.getlong(0)
, mbb.get(outputarray,8,outputarray.length)

but failing @ place (2). suggestions?

try

mbb.put(destarray, 0, sourcearray.length) 

i don't think want start writing @ 8 byte offset, otherwise you'd trying write 8 bytes on lenght of array.