A Little Java Help

[Monster Ahhhhh]

At http://javaboutique.internet.com/tutorials/Java_Game_Programming/LandscapeEng.html
i have found something i want to use in a game im making but dont get how its
done i have been poking at it for a while and im kinda struggling in arrays. I will show the code changed a little because i don't need most of the color stuff. If someone can breakdown how this works it would be appreciated.

public void generateLandscape ()
{

      /* initialize plus, this variable tells you which value will be added or subtracted from the last value. */
      plus = 1;

      // initialize variable factor which decides if + or - value of plus faktor = 1; // Initializing start value of the surface
      start = Math.abs(300 + (rnd.nextInt() % 50));

      // Store start value on the first position in the array
      map [0] = start;

      // Initializing start values for the colors
      int greenvalue = 200;
      int redvalue = 0;
      int bluevalue = 0;

      // Storing first RGB value in the Color array
      colors [0] = new Color (redvalue, greenvalue, bluevalue);

      // Loop to initialize all array positions
      for (int i = 1; i < mapsize; i ++)
      {
            // get the value before the actual position and store it in last
            last = map [i - 1];

            // Decision if changing direction or not
            change = Math.abs(rnd.nextInt() % 10);
            // changing direction and possibly plus
            if (change > 8)
            {
                  // Ändern der Richtung
                  faktor = - (faktor);

                  // new plus (value 1 or 2)
                  plus = 1 + Math.abs(rnd.nextInt() % 2);
            }

            /* Make sure that surface values stay in a certain range */ if (last > 350 || last < 120)
            {
                  // Ändern der Richtung
                  faktor = - (faktor);
            }

           

            // Calculate and store surface value on position i
            map [i] = last + (faktor * plus);

            // Calculate and store color value on position i
            greenvalue = greenvalue + (-faktor * plus);
            colors [i] = new Color (redvalue, greenvalue, bluevalue);
      } 

}