Compare Name field of two object list without loop

Question

I have two Lists(Object) List A has 5 records and List b has 19000 records. What i want to do is compare the name field of list a with that of B. it list b consists of the same name as A, then i want to add it to a 3 rd list. I will not be able to use a nested loop because it is exceeding the time limit. is there any way to do this?

Answer 1

to avoid nested loops exctract needed names of records to Set. After that iterate listA, and if Set with names contains such name, add that record to listC(third list)

Set<String> listBNames = new Set<String>();
for(Sobject sobj :listB){
    listBNames.add(sobj.Name);
}
List<Sobject> listC = new List<Sobject>();
for(Sobject sobj :listA){
    if(listBNames.contains(sobj.Name)){
        listC.add(sobj);
    }
}