Here you can find the source of toLowerCase(final String[] strings)
public static final synchronized String[] toLowerCase(final String[] strings)
//package com.java2s; //License from project: Open Source License public class Main { public static final synchronized String[] toLowerCase(final String[] strings) { String[] lowerCaseStrings = new String[strings.length]; for (int i = 0; i < strings.length; i++) { lowerCaseStrings[i] = strings[i].toLowerCase(); }/*from w ww . ja v a 2 s . c om*/ return lowerCaseStrings; } }