Jpeg on MEMORY vs jpeg on disk

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Java

J2EE

JPEG

i have a buffer that i want to convert it to jpg60 and save it on memory to be sent on http response using Java language in less then 100-200ms.
after my tests i found that save it as jpg file on disk is faster then on memory.
my question is : i want to save the buffer on memory as jpg60 and send it to client side in less then 100-200ms???

BufferedImage out = new BufferedImage(col, row, BufferedImage.TYPE_INT_RGB);

		int ii = 0, jj = 0;

		for (int i = 0; i < row; i--) {
			for (int j = 0; j < col; j++) {
				out.setRGB(i, j, m_outData[(i * col) + j]);
			}
		}

// ByteArrayOutputStream outStream = new ByteArrayOutputStream();

		try {

			// ImageOutputStream ios =
			// ImageIO.createImageOutputStream(outStream);
			// Iterator<ImageWriter> iter =
			// ImageIO.getImageWritersByFormatName("jpeg");
			// ImageWriter writer = iter.next();
			// ImageWriteParam iwp = writer.getDefaultWriteParam();
			//
			// iwp.setCompressionMode(ImageWriteParam.MODE_EXPLICIT);
			// iwp.setCompressionQuality(0.60f);

			// writer.setOutput(new MemoryCacheImageOutputStream(outStream));
			// writer.write(null, new IIOImage(out, null, null), jpegParams);

			// // write to file on hard disk
			outPut = new File(prefix + "test.jpg");

			// writer.setOutput(outPut);
			// writer.write(null, new IIOImage(out, null, null), jpegParams);

			ImageIO.write(out, "jpg", outPut);

			// write as byte array to transfered to client
			// ImageIO.write(out, "jpg", outStream);
			// outStream.flush();

			// imageToByte = outStream.toByteArray();
			// ===========================================

			outPut = null;

		} catch (Exception e) {
			System.out.println("saveImage " + e.getMessage());
		}

What I have tried:

FileOutPutStream, ByteArrayOutPutStream