Java tutorial
//package com.java2s; import java.util.ArrayList; import java.util.List; import java.util.Map; public class Main { public static <T> List<T> unwrap(Map<String, List<T>> response, String key) { if (response != null && response.containsKey(key) && response.get(key) != null) { return response.get(key); } else { return new ArrayList<>(); } } }