关于两个List组合成为一个新List的问题！

import java.util.HashMap;

import java.util.LinkedList;

import java.util.List;

import java.util.Map;

import java.util.Set;

import java.util.TreeMap;



/**

 * ListMapTest - joinListMap

 * @author SageZk

 */

public class ListMapTest {



	public static List<Map<String, String>> joinListMap(List<Map<String, String>>a, List<Map<String, String>> b) {

		if (a == null || b == null) return null;

		if (a.isEmpty() || b.isEmpty()) return null;

		List<Map<String, String>> r = new LinkedList<Map<String, String>>();

		Map<String, List<Map<String, String>>> map = new TreeMap<String, List<Map<String, String>>>();

		for (Map<String, String> ma : a) {

			String date = ma.get("date");

			if (!map.containsKey(date)) map.put(date, new LinkedList<Map<String, String>>());

			map.get(date).add(ma);

		}

		Set<String> set = map.keySet();

		for (String d : set) {

			List<Map<String, String>> la = map.get(d);

			for (Map<String, String> mb : b) {

				String numb = mb.get("num");

				boolean flag = true;

				for (Map<String, String> ma : la) {

					String numa = ma.get("num");

					if (numa.equals(numb)) {

						r.add(new HashMap<String, String>(ma));

						flag = false;

						break;

					}

				}

				if (flag) {

					Map<String, String> tm = new HashMap<String, String>(la.get(0));

					tm.put("num", numb);

					tm.put("money", "");

					r.add(tm);

				}

			}

		}

		return r;

	}



	public static void main(String[] args) {

		Map<String, String> map = null;

		//List 1

		List<Map<String, String>> la = new LinkedList<Map<String, String>>();

		map = new HashMap<String, String>();

		map.put("date", "20080701");

		map.put("num", "101");

		map.put("money", "1000");

		la.add(map);

		map = new HashMap<String, String>();

		map.put("date", "20080701");

		map.put("num", "102");

		map.put("money", "2000");

		la.add(map);

		map = new HashMap<String, String>();

		map.put("date", "20080702");

		map.put("num", "101");

		map.put("money", "3000");

		la.add(map);

		//List 2

		List<Map<String, String>> lb = new LinkedList<Map<String, String>>();

		map = new HashMap<String, String>();

		map.put("num", "101");

		lb.add(map);

		map = new HashMap<String, String>();

		map.put("num", "102");

		lb.add(map);

		map = new HashMap<String, String>();

		map.put("num", "103");

		lb.add(map);

		//List Result

		List<Map<String, String>> r = joinListMap(la, lb);

		if (r != null) {

			System.out.println(r.size());

			for (Map<String, String> m : r) {

				String s = "";

				s += "date:";

				s += m.get("date");

				s += " ; num:";

				s += m.get("num");

				s += " ; money:";

				s += m.get("money");

				System.out.println(s);

			}

		} else {

			System.out.println("Result List is null");

		}

	}



}

6

date:20080701 ; num:101 ; money:1000

date:20080701 ; num:102 ; money:2000

date:20080701 ; num:103 ; money:

date:20080702 ; num:101 ; money:3000

date:20080702 ; num:102 ; money:

date:20080702 ; num:103 ; money: