Member Avatar for johndoe444 
Set s = new HashSet();
if (s.retainAll(anotherSet)) {
     ...
}

now it anotherSet is null the code is showing nullPointerExcpetion. How can I make retainAll work whether anotherSet is null or not?

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  • Latest Post Latest Post by ~s.o.s~
Member Avatar for ~s.o.s~

1. Write your own retainAll() wrapper method which performs a NULL check since the one present in AbstractCollection doesn't.
2. Manually perform a NULL check

if(anotherSet != null && set.retainAll(anotherSet)) { // something }
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