nullpointerexception - Dealing with a null attribute using java 8 streams and sorting using lambda expressions -

let's consider parent class contains 1 integer attribute. created 6 objects of parent class , values of attribute 100, 20, 300, 400, 500, null.

now added objects list(name of list list). want objects attribute value greater 100. used java 8 streams purpose.

predicate<entity> predicate = e -> e.getparentid() < 100; result = list.stream().filter(predicate).collect(collectors.tolist()); 

i want sort list in descending order. used following code purpose.

comparator<entity> comp = (d1,d2) -> d2.getid().compareto(d1.getid()); list.sort(comp); 

in both cases nullpointerexception.

how handle this?

all of answers here revolve around "throw out bad elements, have null getparentid()." may answer, if indeed bad. there's alternative: comparators.nullsfirst (or last.) allows compare things treating null value being less (or greater than) non-null values, don't have throw elements null parentid away.

comparator<entity> cmp = nullslast(comparing(entity::getparentid)); list<entity> list = list.stream().sorted(cmp).collect(tolist()); 

you can similar thing filtering; define predicate as:

predicate<entity> predicate = e -> e.getparentid() != null                                         && e.getparentid() < 100;