请教一个排序问题

xiaozhao32 2008-09-12 11:39:42

现在获得一个List<Map<String,Object> 内容如下：
{id=ddd, name=444, p=A02}
{id=bbb, name=222, p=B01}
{id=ccc, name=333, p=C01}
{id=aaa, name=111, p=A01}
{id=eee, name=555, p=C02}
...

我希望按照Map中的p排序, 然后返回List结果是：
{id=aaa, name=111, p=A01}
{id=bbb, name=222, p=B01}
{id=ccc, name=333, p=C01}
{id=ddd, name=444, p=A02}
{id=eee, name=555, p=C02}
...
谢谢～

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johnsoncr 2008-09-12

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让你要放进List的对象implements Comparator<T>
然后按你的需要实现compare(T arg0, T arg1)方法

sjkof 2008-09-12

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[Quote=引用 2 楼 xiaozhao32 的回复:]
TreeMap 排的序是A01 A02 B01 B02...
好像不大行。。
[/Quote]

你这个排序不是标准的排序,要自己写

xiaozhao32 2008-09-12

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TreeMap 排的序是A01 A02 B01 B02...
好像不大行。。

smsqj 2008-09-12

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Set s = props.keySet();
s = new TreeSet(s);

利用TreeSet可以自动排序。

因为：TreeMap则是对键按序存放

xiaozhao32 2008-09-12

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谢谢楼上 3Q~

mayuanfei 2008-09-12

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

    	Map<String, Object> map1 = new Hashtable<String, Object>();

    	map1.put("id", "ddd");map1.put("name", "444");map1.put("p", "A02");

    	Map<String, Object> map2 = new Hashtable<String, Object>();

    	map2.put("id", "bbb");map2.put("name", "222");map2.put("p", "B01");

    	Map<String, Object> map3 = new Hashtable<String, Object>();

    	map3.put("id", "ccc");map3.put("name", "333");map3.put("p", "C01");

    	Map<String, Object> map4 = new Hashtable<String, Object>();

    	map4.put("id", "aaa");map4.put("name", "111");map4.put("p", "A01");

    	Map<String, Object> map5 = new Hashtable<String, Object>();

    	map5.put("id", "eee");map5.put("name", "555");map5.put("p", "C02");

    	list.add(map1);list.add(map2);list.add(map3);list.add(map4);list.add(map5);

    	

    	Collections.sort(list, new Comparator(){

			public int compare(Object o1, Object o2) {

				Map<String, Object> m1 = (Map<String, Object>) o1;

				Map<String, Object> m2 = (Map<String, Object>) o2;

				return m1.get("p").toString().compareTo(m2.get("p").toString());

			}

    	});

    	for(Map<String, Object> map : list) {

    		System.out.println(map.get("id")+"\t"+map.get("name")+"\t"+map.get("p"));

    	}

    }

mayuanfei 2008-09-12

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{id=ddd, name=444, p=A02}
{id=bbb, name=222, p=B01}
{id=ccc, name=333, p=C01}
{id=aaa, name=111, p=A01}
{id=eee, name=555, p=C02}
上面的数据是在一个Map中,还是list的每个Map就是一行

smsqj 2008-09-12

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打印结果：
{aaa,111,A01}
{bbb,222,A02}
{ccc,333,A03}
{ddd,444,A04}
{eee,555,A05}

smsqj 2008-09-12

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我编了以下代码,希望能给你启发：

import java.util.ArrayList;

import java.util.Collection;

import java.util.Iterator;

import java.util.List;

import java.util.Map;

import java.util.TreeMap;



class Stu{

	String id = "";

	String name = "";

	String p = "";

	public Stu(String id,String name,String p){

		this.id = id;

		this.name = name;

		this.p = p;

	}

	public String getId() {

		return id;

	}

	public void setId(String id) {

		this.id = id;

	}

	public String getName() {

		return name;

	}

	public void setName(String name) {

		this.name = name;

	}

	public String getP() {

		return p;

	}

	public void setP(String p) {

		this.p = p;

	}

}

public class ListMap {

	public static void main(String[] args) {

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

		Map <String,Stu> mapStu = new TreeMap <String,Stu>();

		Stu stu1 = new Stu("ddd","444","A04");

		Stu stu2 = new Stu("aaa","111","A01");

		Stu stu3 = new Stu("ccc","333","A03");

		Stu stu4 = new Stu("eee","555","A05");

		Stu stu5 = new Stu("bbb","222","A02");

		mapStu.put(stu1.getP(), stu1);

		mapStu.put(stu2.getP(), stu2);

		mapStu.put(stu3.getP(), stu3);

		mapStu.put(stu4.getP(), stu4);

		mapStu.put(stu5.getP(), stu5);

		Collection<Stu> colSut = mapStu.values();

		Iterator its = colSut.iterator();

		while(its.hasNext()){

			Stu s = (Stu)its.next();

			System.out.println("{"+s.getId()+","+s.getName()+","+s.getP()+"}");

		}

	}

}