How can I check if an ArrayList contains any element of another ArrayList?

Question

Is there any way to determine whether an ArrayList contains any element of a different ArrayList?

Like this:

list1.contains(any element of list2)

Is looping through all the elements of list2 and checking the elements one by one the only way?

If 'X contains an element of Y' is the main usecase for your collection, you may want to consider using Set instead. — maasg, Sep 22 '13 at 12:41

score 64 · Answer 1 · answered Nov 27 '13 at 13:51

64

Consider the following: Java SE 7 documentation: java.util.Collections.disjoint

The "disjoint" method takes two collections (listA and listB for example) as parameters and returns "true" if they have no elements in common; thus, if they have any elements in common, it will return false.

A simple check like this is all that's required:

if (!Collections.disjoint(listA, listB))
{
  //List "listA" contains elements included in list "listB"
}

answered Nov 27 '13 at 13:51

Fallso

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very useful method 1.7 onwards... :D – ArifMustafa Oct 14 '17 at 18:01
I prefer this answer as it uses native Java methods only and there is no casting required. – Ernani Sep 17 '19 at 13:29

score 8 · Accepted Answer · answered Sep 22 '13 at 12:40

8

Although not highly efficient, this is terse and employs the API:

if (!new HashSet<T>(list1).retainAll(list2).isEmpty())
    // at least one element is shared

answered Sep 22 '13 at 12:40

Bohemian

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score 5 · Answer 3 · answered Sep 22 '13 at 12:46

5

if(!CollectionUtils.intersection(arrayList1, arrayList2).isEmpty()){
      // has common
}
else{
   //no common
}

use org.apache.commons.collections

answered Sep 22 '13 at 12:46

Trying

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score 4 · Answer 4 · edited Sep 23 '22 at 20:03

4

If you have access to Apache Commons, see CollectionUtils.intersection(a,b)

Use like this:

! CollectionUtils.intersection(list1, list2).isEmpty()

edited Sep 23 '22 at 20:03

halfer

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answered Sep 22 '13 at 12:43

vikingsteve

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Rahul Tripathi · Answer 5 · 2013-09-22T12:51:36.700

3

How about trying like this:-

List1.retainAll(List2)

like this:-

int a[] = {30, 100, 40, 20, 80};
int b[] = {100, 40, 120, 30, 230, 10, 80};
List<Integer> 1ist1=  Arrays.asList(a);
List<Integer> 1ist2=  Arrays.asList(b);
1ist1.retainsAll(1ist2);

edited Sep 22 '13 at 12:51

answered Sep 22 '13 at 12:39

Rahul Tripathi

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score 1 · Answer 6 · answered Sep 22 '13 at 12:45

If you're not constrained in using third-party libraries, Apache commons ListUtils is good for common list operations.

In this case you could use the intersection method

if(!ListUtils.intersection(list1,list2).isEmpty()) {
    // list1 & list2 have at least one element in common
}

How can I check if an ArrayList contains any element of another ArrayList?

6 Answers6

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