How to check if a string contains an element from a list

Question

What is the best way to check if a string contains an element from a list?

for example:

String email= 'itairu@gmail.com'
List<String> domainNames = split by ; from domains in a custom setting 

for example : (domainNames = [0] - gmail.com, [1] - example.com, [2] - mof.com);

How can I check if email field is contains one of the values in the domainName's List?

I can do it with a Boolean field that will be turned to true if one of field is found for this case -

boolean found = false;
for(String s : domainNames ){
 if(email.contains(s)){
   found =true;  
 }

}

I want to know if there is a better way - in case I will have a huge amount of values to move on in the for loop for this.

Thanks!

Answer 1

A shorter version of your code just checks the domain directly:

Boolean found = domainNames.contains(email.split('@',2)[1]);

There's other ways to do this, too, but this is probably the most straightforward version.

Answer 2

If you have control over the type of domainNames, you should consider changing its type to Set<string>. Sets hash their values, so checking whether they contain a particular value takes the same amount of time regardless of the number of elements in the set, compared to a List which must go through each element until it finds one that matches.

Set<String> domainNames = new Set<String>{'example.com', 'gmail.com'};
domainNames.contains(email.split('@', 2)[1]);

Also, the general solution to the question of whether a particular string contains any strings in a list where they could be in any part of the input string would be to do what you did, except you would use a break statement to end the loop once you've found a match:

boolean found = false;
for(String s : domainNames ){
     if(email.contains(s)){
         found = true;  
         break;
     }
}