Here you can find the source of toStrings(Collection> c)
public static List<String> toStrings(Collection<?> c)
//package com.java2s; // the GNU General Public License. import java.util.ArrayList; import java.util.Collection; import java.util.List; public class Main { public static List<String> toStrings(Collection<?> c) { List<String> result = new ArrayList<String>(c.size()); for (Object e : c) { result.add(e.toString());//from w w w . j a v a2s . c o m } return result; } }