Use the ByteArrayInputStream to read the contents of the input stream into
the buffer used to construct a ByteArrayInputStream .
Later you can then get your data  back by accessing the buffer.

but java API says that ByteArrayInputStream's construtor does not
copy the buffer.

what the other guy meant by copying to a buffer was that u create a array of
type Byte, and copy  data from ur stream there using ByteArrayInputStream, ok

but, the read method of InputStream returns int type , how can i make
byte[] type from it?

if u read correctly, it returns lower end byte values only, ie integers
within byte range. Also as u must be aware byte is a subset on int only and
all bytes are coverted to int for all calculation purposes...thats why
method return type is int, you can always store it in byte array using type
casting,