gistfile1.java

class ChangeAtomSymbol extends AbstractUndoableEdit {

    IAtomContainer container;
    IAtom remove, replace;

    ChangeAtomSymbol(IAtomContainer container,
                     IAtom original,
                     String newSymbol) {

        Atom copy = new Atom(original); // do not clone!
        copy.setSymbol(newSymbol);

        this.container = container;
        this.remove = original;
        this.replace = copy;

    }

    @Override
    public void undo() throws CannotUndoException {
        // undo: remove the replace atom and add the remove back in
        container.removeAtom(replace);
        container.addAtom(remove);

        // replace in bonds
        for (IBond bond : container.getConnectedBondsList(replace)) {
            for (int i = 0; i < bond.getAtomCount(); i++) {
                if (bond.getAtom(i) == replace) { // object equivalence
                    bond.setAtom(remove, i);      // swap out the bond
                }
            }
        }
        
        // replace in electron containers... 
        
    }

    @Override
    public void redo() throws CannotRedoException {
        // do the opposite of above
    }
}