Java - Image Rotation

It is not enough to switch the width and height of the image. You are rotating using the center of the image as the origin of rotation. Just try the same with a sheet of paper and you will see it works the same way. You must also move the paper a little bit, which means to apply a transform to fix this. So, immediately after the rotate call, do this:

  graphics.translate((newImage.getWidth() - oldImage.getWidth()) / 2, (newImage.getHeight() - oldImage.getHeight()) / 2);