Convert InputStream to byte array in Java

Question

How do I read an entire InputStream into a byte array?

Answer 1

You can use Apache Commons IO to handle this and similar tasks.

The IOUtils type has a static method to read an InputStream and return a byte[].

InputStream is; byte[] bytes = IOUtils.toByteArray(is); 

Internally this creates a ByteArrayOutputStream and copies the bytes to the output, then calls toByteArray(). It handles large files by copying the bytes in blocks of 4KiB.

Answer 2

You need to read each byte from your InputStream and write it to a ByteArrayOutputStream.

You can then retrieve the underlying byte array by calling toByteArray():

InputStream is = ... ByteArrayOutputStream buffer = new ByteArrayOutputStream();  int nRead; byte[] data = new byte[16384];  while ((nRead = is.read(data, 0, data.length)) != -1) {   buffer.write(data, 0, nRead); }  return buffer.toByteArray();