How to check if element in groovy array/hash/collection/list?

Question

How do I figure out if an array contains an element? I thought there might be something like [1, 2, 3].includes(1) which would evaluate as true.

Solution 1

.contains() is the best method for lists, but for maps you will need to use .containsKey() or .containsValue()

[a:1,b:2,c:3].containsValue(3)
[a:1,b:2,c:3].containsKey('a')

Solution 2

Some syntax sugar

1 in [1,2,3]

Solution 3

For lists, use contains:

[1,2,3].contains(1) == true

Solution 4

If you really want your includes method on an ArrayList, just add it:

ArrayList.metaClass.includes = { i -> i in delegate }

Solution 5

You can use Membership operator:

def list = ['Grace','Rob','Emmy']
assert ('Emmy' in list)  

Membership operator Groovy

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Comments

[Atharva Johri]

Can you find the index out also of where this equal element is in the list?

[Thomas Traude]

@AtharvaJohri assert [12,42,33].indexOf(42) == 1

[Harshay Buradkar]

Probably you wanted to say [1,2,3].contains(1). Because I am guessing contains function itself already returns a boolean. Why do you want to again compare it with a hardcoded 'true'.

[Automatico]

@HarshayBuradkar To make really sure true == true, of course #joke

[Jesse Glick]

Careful. def m = [a: true]; 'a' in m → true yet def m = [a: false]; 'a' in m → false!

[Naeel Maqsudov]

And, in addition, to check if a map contains some not null value under a certain key, it is enough to check the following expression if(aMap["aKey"]==aValue).

[Big McLargeHuge]

How do you negate this?

[Leponzo]

@BigMcLargeHuge !(1 in [1,2,3])

[Gaurav]

works flawlessly!

[wiredniko]

The way to deal with [a:false] is to use contains. [a: false].containsKey('a') -> true