I have a list testEle which contains 100 elements. I am iterating over it an need to filter only the values which contains anyone of elements in second list finalList {a1,a2,a3...so on}

testEle.stream().filter( x -> x.matches(// any one of finalList element here))

I am not sure what should be inside the .matches() or if I should be using something else ?

CodePudding user response：

matches is a String function to test a regular expression on it. Just check with List::contains.

testEle.stream().filter( x -> finalList.contains(x))

CodePudding user response：

I have a list testEle which contains 100 elements. I am iterating over it an need to filter only the values which contains anyone of elements in second list finalList.

Since contain() check has a cost O(n) depending on the size of the finalList it might make sense to store its values into a HashSet and perform checks against the set.

Set<Foo> set = new HashSet<>(finalList);
        
testEle.stream().filter(set::contains)...

From the OP's comment:

I need case insensitive comparison. So how to do that ? finalList.contains.equalsIgnoreCase type something

Then you can create a stream over the finalList inside the filter and apply Stream.anyMacth() as a terminal operation of the nested stream.

List<Foo> finalList = // initializing the list
        
testEle.stream().filter(x -> 
        finalList.stream().anyMatch(y -> y.equalsIgnoreCase(x))
    )...