java – NullPointerException：Collections. binarySearch(List <？extends T>,T,Comparator <？super T>)line：not available

Print this stack error "collections. Binarysearch (list , t, comparator ) line: not available"

int index = Collections.binarySearch(getEmails(),email,determineComparator());
     // Search where to insert

I think the e-mail (returned by getemails()) may be null, but it is instantiated as:

ArrayList<Email> emails= new ArrayList<Email>();

If you point out what you need, I can provide more details

Solution

Your getemails () implementation must return null Collections. Binarysearch can handle null comparators but cannot handle empty lists