java - Find disjoint set irrespective of case of the strings -

i using collection.disjoint find disjoint set of 2 string collections c1, c2. not ignore cases, example - string str different str.

return collections.disjoint(c1, c2); 

can find disjoint of both collections ignoring cases without using loop?

if absolutely insist no for loop used, can find disjoint between 2 collections of lowercased strings. using google guava, should like:

package ru.zombator.stackoverflow;  import java.util.arrays; import java.util.collection; import java.util.collections; import java.util.locale;  import com.google.common.base.function; import com.google.common.collect.collections2;  public final class disjointignorecase {     public static void main(string[] args) {         collection<string> coll1 = arrays.aslist("donald", "duck");         collection<string> coll2 = arrays.aslist("donald", "donut");         collection<string> coll3 = arrays.aslist("homer", "donut");         collection<string> coll4 = arrays.aslist("donald", "duck");          // print false         system.out.println(disjointignorecase(coll1, coll2));         system.out.println(disjointignorecase(coll2, coll3));         system.out.println(disjointignorecase(coll1, coll4));          // print true (no common elements)         system.out.println(disjointignorecase(coll1, coll3));     }             private static boolean disjointignorecase(collection<string> coll1, collection<string> coll2) {         return collections.disjoint(lowercased(coll1), lowercased(coll2));     }             private static collection<string> lowercased(collection<string> coll) {         return collections2.transform(coll, new function<string, string>() {             @override             public string apply(string input) {                 return input.tolowercase(locale.us);             }         });     } }