content: /*
   * Copyright (c) 2016, Alex Blewitt, Bandlem Ltd
   * Copyright (c) 2016, Packt Publishing Ltd
   *
   * All rights reserved. This program and the accompanying materials
   * are made available under the terms of the Eclipse Public License v1.0
   * which accompanies this distribution, and is available at
   * http://www.eclipse.org/legal/epl-v10.html
   */
  package com.packtpub.e4.clock.ui.internal;
  
  import java.time.ZoneId;
  import java.util.Comparator;
  import java.util.Map;
  import java.util.Set;
  import java.util.TreeMap;
  import java.util.TreeSet;
  import java.util.function.Supplier;
  import java.util.stream.Collectors;
  
  public class TimeZoneComparator implements Comparator<ZoneId> {
  	public int compare(ZoneId o1, ZoneId o2) {
  		return o1.getId().compareTo(o2.getId());
  	}
  
  	public static Map<String, Set<ZoneId>> getTimeZones() {
  		Supplier<Set<ZoneId>> sortedZones = () -> new TreeSet<>(new TimeZoneComparator());
  		return ZoneId.getAvailableZoneIds().stream() // stream
  				.filter(s -> s.contains("/")) // with / in them
  				.map(ZoneId::of) // convert to ZoneId
  				.collect(Collectors.groupingBy( // and group by
  						z -> z.getId().split("/")[0], // first part
  						TreeMap::new, Collectors.toCollection(sortedZones)));
  	}
  }