test.java

Especially critical is high temporary memory usage in enterprise applications, which can have a high number of concurrent users. Because it can happen out of the blue, this OutOfMemoryError is especially troublesome, as it cannot be countered with a nightly reboot. The following code illustrates the problem:

byte[] image = getTheByteImage();
response.setContentType("image/jpeg");
ServletOutputStream out = response.getOutputStream();
out.write(image);
out.flush();
out.close();

While it is not that obvious, the code consumes memory on heap for each image before sending it to the browser. A much better variant would be to stream the image like this:

InputStream image = getTheImageAsStream();
response.setContentType("image/jpeg");
ServletOutputStream out = response.getOutputStream();
IOUtils.copy(image, out);
out.flush();
out.close();
(Of course BufferedStreams and IOUtils use byte[] internally as well, but this is much smaller)