Here you can find the source of getLetter()
private static String getLetter()
//package com.java2s; //License from project: Open Source License import java.util.concurrent.ThreadLocalRandom; public class Main { private static String letter = ""; private static String getLetter() { String[] let = { "a", "b", "c", "d", "e", "f", "g", "h", "i", "j", "k", "l", "m", "n", "o", "p", "q", "r", "s", "t", "u", "v", "w", "x" + "y" + "z" }; letter = let[ThreadLocalRandom.current().nextInt(let.length)]; return letter; }/*from ww w .j a v a 2 s .c o m*/ }