I'm having quite a problem here, and I think it is because I don't understand very much how I should use the API provided by Java.
I need to write an int
and a byte[]
into a byte[]
.
I thought of using a DataOutputStream
to solve the data writing with writeInt(int i)
and write(byte[] b)
, and to be able to put that into a byte array, I should use ByteArrayOutputStream
method toByteArray().
I understand that this classes use the Wrapper pattern, so I had two options:
DataOutputStream w = new DataOutputStream(new ByteArrayOutputStream());
or
ByteArrayOutputStream w = new ByteArrayOutputStream(new DataOutputStream());
but in both cases, I "loose" a method. in the first case, I can't access the toByteArray()
method, and in the second, I can't access the writeInt()
method.
How should I use this classes together?
Like this:
ByteArrayOutputStream baos = new ByteArrayOutputStream();
DataOutputStream w = new DataOutputStream(baos);
w.writeInt(100);
w.write(byteArray);
w.flush();
byte[] result = baos.toByteArray();
Actually your second version will not work at all. DataOutputStream
requires an actual target stream in which to write the data. You can't do new DataOutputStream()
. There isn't actually any constructor like that.