How to lowercase every element of a collection efficiently?

Question

What's the most efficient way to lower case every element of a List or Set?

My idea for a List:

final List<String> strings = new ArrayList<String>(); strings.add("HELLO"); strings.add("WORLD");  for(int i=0,l=strings.size();i<l;++i) {   strings.add(strings.remove(0).toLowerCase()); } 

Is there a better, faster way? How would this example look like for a Set? As there is currently no method for applying an operation to each element of a Set (or List) can it be done without creating an additional temporary Set?

Something like this would be nice:

Set<String> strings = new HashSet<String>(); strings.apply(   function (element)   { this.replace(element, element.toLowerCase();) }  ); 

Thanks,

Answer 1

Yet another solution, but with Java 8 and above:

List<String> result = strings.stream()                              .map(String::toLowerCase)                              .collect(Collectors.toList());