一道8K的面试题

import java.util.*;

public class TestCreateMap {
	public static void main(String[] args) {
		List<String> myList = myList();
		Set<String> mySet = mySet();
		List<String> d1 = new ArrayList<String>();
		Map<String, List<String>> myMap = new LinkedHashMap<String, List<String>>();
		
		Iterator i = mySet.iterator();		
		while (i.hasNext()) {			
			String key = (String)i.next();			
			
			for (String value : myList) {
				String[] str = value.split("\\$\\$\\$");
				if (str[0].contains(key)) {					
					d1.add(str[1]);
				}					
			}			
			System.out.println(d1);			
			myMap.put(key, d1);
			d1.clear();	
		}
		System.out.println(myMap);
	}		
	
	public static List myList() {
		List<String> list = new ArrayList<String>();
		list.add("###20110810$$$hello3434334343443hhh20110810");
		list.add("###20110810$$$world3434334343443hhh20110810");
		
		list.add("###20110811$$$hello3434334343443hhh20110811");
		list.add("###20110811$$$world3434334343443hhh20110811");
		
		list.add("###20110812$$$hello3434334343443hhh20110812");
		list.add("###20110812$$$world3434334343443hhh20110812");
		
		list.add("###20110813$$$hello3434334343443hhh20110813");
		list.add("###20110813$$$world3434334343443hhh20110813");
		
		list.add("###20110814$$$hello3434334343443hhh20110814");
		list.add("###20110814$$$world3434334343443hhh20110814");
		
		list.add("###20110815$$$hello3434334343443hhh20110815");
		list.add("###20110815$$$world3434334343443hhh20110815"); 
		
		return list;
	}
	
	public static Set mySet() {
		Set<String> set = new LinkedHashSet<String>();
		set.add("20110810");
		set.add("20110811");
		set.add("20110812");
		set.add("20110813");
		set.add("20110814");
		set.add("20110815");
		
		return set;
	}
}

 修改几楼的朋友的其中一段代码，有个疑问打印 d1 是有值的，为什么打印 myMap 值为空，键正常