Remove null items from a list in Groovy
GroovyGroovy Problem Overview
What is the best way to remove null items from a list in Groovy?
ex: [null, 30, null]
want to return: [30]
Groovy Solutions
Solution 1 - Groovy
Just use minus:
[null, 30, null] - null
Solution 2 - Groovy
here is an answer if you dont want to keep the original list
void testRemove() {
def list = [null, 30, null]
list.removeAll([null])
assertEquals 1, list.size()
assertEquals 30, list.get(0)
}
in a handy dandy unit test
Solution 3 - Groovy
The findAll method should do what you need.
[null, 30, null].findAll {it != null}
Solution 4 - Groovy
I think you'll find that this is the shortest, assuming that you don't mind other "false" values also dissappearing:
println([null, 30, null].findAll())
> public Collection findAll() finds the items matching the IDENTITY
> Closure (i.e. matching Groovy truth).
>
> Example:
>
> def items = [1, 2, 0, false, true, '', 'foo', [], [4, 5], null]
> assert items.findAll() == [1, 2, true, 'foo', [4, 5]]
Solution 5 - Groovy
This can also be achieved by grep:
assert [null, 30, null].grep() == [30]
or
assert [null, 30, null].grep {it} == [30]
or
assert [null, 30, null].grep { it != null } == [30]
Solution 6 - Groovy
Simply [null].findAll{null != it} if it is null then it return false so it will not exist in new collection.
Solution 7 - Groovy
Another way to do it is [null, 20, null].findResults{it}.
Solution 8 - Groovy
This does an in place removal of all null items.
myList.removeAll { !it }
If the number 0 is in your domain you can check against null
myList.removeAll { it == null }