Array contains() without case sensitive lookup?

Question

Can I somehow tell the array.contains() method to not make the lookup case sensitive?

List<String> data = Arrays.asList(
  "one", Two", "tHRee"); //lots of entries (100+)

data.contains("three");

Convert everything to lowercase before inserting into `data` and before looking up? — NPE, Mar 07 '13 at 11:17
http://stackoverflow.com/questions/8751455/arraylist-contains-case-sensitivity — Peter Jaloveczki, Mar 07 '13 at 11:18
If the values in list are unique you can use `TreeSet` with [case insensitive comparator](http://docs.oracle.com/javase/1.5.0/docs/api/java/lang/String.html#CASE_INSENSITIVE_ORDER) — Esailija, Mar 07 '13 at 11:18

Averroes · Accepted Answer · 2017-05-12T11:54:15.357

50

contains just check if an object is present in the List. So you can't do a case insensitive lookup here, because "three" is a different object than "Three".

A simple approach to solve this would be

public boolean containsCaseInsensitive(String s, List<String> l){
     for (String string : l){
        if (string.equalsIgnoreCase(s)){
            return true;
         }
     }
    return false;
  }

and then

containsCaseInsensitive("three", data);

Java 8+ version:

public boolean containsCaseInsensitive(String s, List<String> l){
        return l.stream().anyMatch(x -> x.equalsIgnoreCase(s));
    }

edited May 12 '17 at 11:54

answered Mar 07 '13 at 11:21

Averroes

4,168
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@membersound - how did you use equalsIgnoreCase for this scenario? – Tim Boland Nov 09 '15 at 23:04
@KishanSolanki - I'm pretty sure it works. What does not work for you? – Averroes May 25 '20 at 06:55

score -1 · Answer 2 · answered Mar 07 '13 at 11:31

-1

it will require you to write your own contains() method. pointers for custom contains():

iterate over all the elements in the list.
compare the parameter string with all the values in
to make comparison case-insensitive be sure to apply any of toLowerCase or toUpperCase on BOTH parameter and the current element.

List list; public boolean contains(String str){
```
   for(int i=0;i<list.size();i++){
       if(list.elementAt(i).toLowerCase().Equals(str.toLowerCase())) return true;
   }
return false;
}
```

answered Mar 07 '13 at 11:31

Ankit

6,554
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3

Not an efficient answer. You are converting `str` to lower case N times (once for each element of `list`), and you are converting each item of `list` to lower case every time you call this method. If you are going to the trouble of writing your own method, just use `equalsIgnoreCase` and skip all of the allocations. – John Hart Jan 04 '16 at 19:26

Array contains() without case sensitive lookup?

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