Here you can find the source of toLowerCase(CharSequence chars)
public static CharSequence toLowerCase(CharSequence chars)
//package com.java2s; public class Main { public static CharSequence toLowerCase(CharSequence chars) { StringBuilder builder = new StringBuilder(); char c;// w ww . jav a 2 s . com for (int i = 0; i < chars.length(); i++) { c = chars.charAt(i); if (Character.isUpperCase(c)) c = Character.toLowerCase(c); builder.append(c); } return builder.toString(); } }