How to get a byte array from FileInputStream without OutOfMemory error

Question

I have a FileInputStream which has 200MB of data. I have to retrieve the bytes from the input stream.

I'm using the below code to convert InputStream into byte array.

private byte[] convertStreamToByteArray(InputStream inputStream) {
    ByteArrayOutputStream bos = new ByteArrayOutputStream();
    try {
        int i;
        while ((i = inputStream.read()) > 0) {
            bos.write(i);
        }
    } catch (IOException e) {
        e.printStackTrace();
    }
    return bos.toByteArray();
}

I'm getting OutOfMemory exception while coverting such a large data to a byte array.

Kindly let me know any possible solutions to convert InputStream to byte array.

Answer 1

Why do you want to hold the 200MB file in memory? What are you going to to with the byte array?

If you are going to write it to an OutputStream, get the OutputStream ready first, then read the InputStream a chunk at a time, writing the chunk to the OutputStream as you go. You'll never store more than the chunk in memory.

eg:

     public static void pipe(InputStream is, OutputStream os) throws IOException {

        int read = -1;
        byte[] buf = new byte[1024];

        try {
            while( (read = is.read(buf)) != -1) {
                os.write(buf, 0, read);
            }
        }
        finally {
            is.close();
            os.close();
        }
    }

This code will take two streams and pipe one to the other.