j2me JPEG library which does not use JSR 234 and can be used on almost any device.
Port of Sun's JIMI image library on j2me.

Usage:

import com.encoder.jpg.*;

//your input image
Image image = Image.createImage(128, 128);

JPGEncoder encoder = new JPGEncoder();
int quality = 65;
byte[] encodedImage = encoder.encode(image, quality);

//now save or send encoded jpeg image