Java 8 String Comparison

Question

I have two list of strings. I want to check if any string from one list is available in another list. Have used below approach which fails.

Please let me know a better approach

List<String> mylist = Arrays.asList(stringArray1);
List<String> items = Arrays.asList(stringArray2);

return mylist.stream().anyMatch(t->items.stream().anyMatch(t::contains));

what do you want to obtain btw? All the entries that are common? — Eugene
– Eugene, Commented Jul 23, 2018 at 13:18
@Eugene I want a boolean value if the any one value is available in another list — Prabhakaran Manickkavachagam
– Prabhakaran Manickkavachagam, Commented Jul 23, 2018 at 13:35
in this case, myList.stream().anyMatch(items::contains) should do the job — Eugene
– Eugene, Commented Jul 23, 2018 at 13:36

Jacob G. · Accepted Answer · 2018-07-23 13:44:50Z

6

If you want to find if any element in mylist exists in items, you can first turn items into a Set:

Set<String> setOfItems = new HashSet<>(items);

Then, you can simply iterative over mylist and check if any element is contained in setOfItems.

mylist.stream().anyMatch(setOfItems::contains);

This brought your O(n * k) problem down to O(n + k) where n and k are the sizes of mylist and items, respectively.

edited Jul 23, 2018 at 13:44

answered Jul 23, 2018 at 13:39

Jacob G.

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2 Comments

Prabhakaran Manickkavachagam Over a year ago

G: Your a Rockstar, Thank you

Holger Over a year ago

You still can use a one-liner, mylist.stream().anyMatch(new HashSet<>(items)::contains);. Since this optimization only pays off for larger collections, it’s even possible to use a threshold, e.g.

static final int HASH_THRESHOLD = 30; … mylist.stream().anyMatch((items.size() < HASH_THRESHOLD? items: new HashSet<>(items))::contains);

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