Here you can find the source of maskNull(List
private static List<String> maskNull(List<String> pTypes)
//package com.java2s; import java.util.*; public class Main { private static List<String> maskNull(List<String> pTypes) { return (pTypes == null) ? Collections.<String>emptyList() : pTypes; }/*w ww . j a v a2 s .com*/ }