Opposite of intersect in groovy collections

问题

what would be the opposite of intersect in groovy collections?

回答1:

You probably want to combine both the answers from @Andre and @denis

I think what you want is the union and then subtract the intersection from this

def a = [1,2,3,4,5]
def b = [2,3,4]

assert [1,5] == ( a + b ) - a.intersect( b )

The solution given by denis would depend on whether you do

def opposite = leftCollection-rightCollection // [1,5]

or

def opposite = rightCollection-leftCollection // []

which I don't think you wanted

回答2:

I'm not certain what you mean by "opposite of union", but my guess is that you mean symmetric difference (AKA set difference or disjunction). The result of this operation is shown in red below.

The easiest way to perform this operation on two Java/Groovy collections is to use the disjunction method provided by Apache commons collections.

回答3:

Could it be this?

def leftCollection = [1,2,3,4,5]
def rightCollection = [2,3,4]
def opposite = leftCollection-rightCollection
println opposite

Prints

[1,5]

回答4:

use intersect for intersections

assert [4,5] == [1,2,3,4,5].intersect([4,5,6,7,8])

use + for unions:

assert [1,2,3,4,5] == [1,2,3] + [4,5]

see http://groovy.codehaus.org/groovy-jdk/java/util/Collection.html

回答5:

(a-b)+(b-a)
// (a-b) return [1,5]
//(b-a) return []
// TOTAL = [1,5]+[]

this is when we have: a=[1,2,3,4,5],b=[2,3,4,5]

OOP :

java.util.List.metaClass.oppIntersect={b->
  return ((delegate-b)+(b-delegate))
}

then

a.oppIntersect(b)

END!

来源：https://stackoverflow.com/questions/5713665/opposite-of-intersect-in-groovy-collections