Wow! One week into java and you are already taking on Image Manipulation. This is a pretty intense topic so make sure you can walk before you run.
I wrote a tutorial on
Image Processing. The theory section may be helpful. Basically, you will be loading each of the images as a
BufferedImage and then iterated through the pixels, constructing two, two dimensional arrays that hold the RGB value of each pixel. Then you need to write a method that compares the two arrays and looks for differences (nested for loops) and returning the results (a two dimensional array of booleans would work). This is the easy part. There are two hard parts. The first is highlighting the differences. You could construct a another image using the first image and the results of the comparison that draws the different pixels yellow for example. The other hard part is trying to identify movement or scaling differences. For example, if you crop the second image by 1 pixel at the top, this algorithm would falsely identify ALL pixels as being altered.
Like I said, image processing is a pretty complex topic so make sure you have the fundamentals down pat before you tackle this assignment.