Java tutorial
//package com.java2s; import java.util.HashMap; public class Main { private static HashMap<Integer, HashMap<Integer, Integer>> createFullAvailableTime() { HashMap<Integer, HashMap<Integer, Integer>> availableTime = new HashMap<>(); for (int hour = 0; hour < 24; hour++) { HashMap<Integer, Integer> minutes = new HashMap<>(60); for (int minute = 0; minute < 60; minute++) { minutes.put(minute, minute); } availableTime.put(hour, minutes); } return availableTime; } }