java的list排序

import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;

public class Test5 {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		// TODO Auto-generated method stub

		List<Map<String, String>> list1 = new ArrayList<Map<String, String>>();

		for (int i = 0; i < 5; i++) {
			Map<String, String> map1 = new HashMap<String, String>();
			if (i != 3) {
				map1.put("a", "" + i);
			}

			map1.put("b", "aaa");

			list1.add(map1);
			System.out.println("map1,"+i+","+map1.get("a")+",");
 
		}

		Collections.sort(list1, new Comparator<Map<String, String>>() {
			//  排序
			public int compare(Map<String, String> o1, Map<String, String> o2) {
				Map m1 = (Map) o1, m2 = (Map) o2;
				// 从m1与m2取字段值然后比较，大于返回1，等于返回0，小于返回-1
 

					if (Float.parseFloat("" + m1.get("a")) > Float
							.parseFloat("" + m2.get("a"))) {
						return -1;
					}
					if (Float.parseFloat("" + m1.get("a")) < Float
							.parseFloat("" + m2.get("a"))) {
						return 1;
					}
		 
				return 0;

			}

		});

		for (Map<String, String> m : list1) {
			System.out.println(m.toString());
		}

	}

}