Here you can find the source of toLowerCase(Collection
public static List<String> toLowerCase(Collection<String> values)
//package com.java2s; // Licensed under the Apache License, Version 2.0 (the "License"); import java.util.ArrayList; import java.util.Collection; import java.util.List; public class Main { public static List<String> toLowerCase(Collection<String> values) { List<String> result = new ArrayList<String>(); for (String value : values) result.add(value.toLowerCase()); return result; }//from w ww.j a v a 2 s . co m }