Modify "add" to pay attention to the value of previousORnext. If it is null, adding should easy. If it is not null, you have to do a comparison to determine if previousORnext is previous or next. Set previous or next to previousORnext and set next or previous using the getNext() or getPrevious method of DLLEntry.

Add newEntry to the list. Be careful: there are special cases if previous or next is null meaning it should be added first or last.

Default Code...

protected DLLEntry add (DLLEntry previousORnext, DLLEntry newEntry) { if(first == null) { first = newEntry; last = newEntry; } else { last.setNext(newEntry); newEntry.setPrevious(last); last = newEntry; }

return newEntry; }

My code, can my code be salvaged? or start from scratch?

protected DLLEntry add (DLLEntry previousORnext, DLLEntry newEntry) { if(first == null) { first = newEntry; last = newEntry; }

//start of my code

if(previousORnext != null) { newEntry.setNext(previousORnext); newEntry.setPrevious(previousORnext.getPrevious()); if(newEntry.getPrevious() != null) { newEntry.getPrevious().setNext(newEntry); } else if(previousORnext == first) { first.setPrevious(newEntry); newEntry.setNext(first); }

//end of my code

else { last.setNext(newEntry); newEntry.setPrevious(last); last = newEntry; } } return newEntry; }

location SortedDLLPD add(location, "Ian","271") entry first last Ian 271 Ann Bob Eve Zoe Jay 182 314 159 264 818 location SortedDLLPD add(location, "Ian","271") entry first last Ian 271 Ann Bob Eve Zoe Jay 182 314 159 264 818