How To Grab Graphical Object From Arraylist And Modify It

I am trying to grab a graphical object from an arraylist, and reposition its coordinates on a Jframe when adding it. My program of course deals with strings, and once it sees specific words in my console, some method is called that adds, removes, or otherwises modifies certain objects on screen.

Here I want to say something like move(object[1],xpos,ypos) which will move a certain object from a specified point in the array, and move it to new x and y positions on the JFrame. I use a different class that extends a graphics program, so when I say add(something,x,y) it draws the object onscreen where I want it. These are some relevant, though incomplete, methods that should move an object already painted on screen:

Console class

Java Code:

public void doMoveCommand(String cmd, String arg, String xpos, String ypos) {
int x = Integer.parseInt(xpos);
int y = Integer.parseInt(ypos);
if (cmd.equals("posMake") && arg.equals("star")) {
box.moveStar(box.historyG.get(1), x, y); //historyG is an arraylist of GPolygons
freeCommand();

[Code] ....

When I say makepos(whatever) I am getting a arraylist out of bounds exception. How I might be able to accomplish moving objects already on screen?