根据分组依据对Java集合元素进行分组

/**
 * 模拟中国电信翼支付的分账功能接口调用的参数字符串
 * 根据分组依据对集合进行分组
 * @author ZhangBing
 */
public class CollectionGroupTest {
    /***
     * 分组依据接口，用于集合分组时，获取分组依据
     * @author ZhangBing
     * @date 20140530
     * @param <T>
     */
    interface GroupBy<T>{
        T groupBy(Object obj);
    }
    /**
     * 模拟订单实体类
     * @author ZhangBing
     *
     */
    private static class ItemInfo{
        private String id;//订单ID
        private String shopid;//店铺ID
        private String fxSplitMoney;//分账金额
        private String itemValue;//物品价格
        /** 省略getter setter方法 */
        .....
    }
    
    /**
     * 集合临时转换类,跟模拟订单实体类对应
     * @author ZhangBing
     * @date 2014-5-30 上午10:38:48
     */
    private static class MyData{
        private String id ;
        private String shopId ;
        private String itemValue;
        private String fxMoney;
        public String getFxMoney(){
            return fxMoney;
        }
        public MyData setFxMoney(String fxMoney){
            this.fxMoney = fxMoney;
            return this;
        }
        public String getItemValue(){
            return itemValue;
        }
        public MyData setItemValue(String itemValue){
            this.itemValue = itemValue;
            return this;
        }
        public String getId() {
            return id;
        }
        public MyData setId(String id) {
            this.id = id;
            return this;
        }
        public String getShopId() {
            return shopId;
        }
        public MyData setShopId(String shopId) {
            this.shopId = shopId;
            return this;
        }
    }
    
    /**
     * 分组依据实现
     * @param <T>
     * @param <D>
     * @param colls
     * @param gb
     * @return
     */
    private static final <T extends Comparable<T>,D> Map<T,List<D>> group(Collection<D> colls,GroupBy<T> gb){
        if(colls == null || colls.isEmpty()){
            System.out.println("分组集合不能为空!");
            return null;
        }
        if(gb == null){
            System.out.println("分组依据接口不能为Null!");
            return null;
        }
        Iterator<D> iter = colls.iterator();
        Map<T,List<D>> map = new HashMap<T, List<D>>();
        while(iter.hasNext()){
            D d = iter.next();
            T t = gb.groupBy(d);
            if(map.containsKey(t)){
                map.get(t).add(d);
            }else{
                List<D> list = new ArrayList<D>();
                list.add(d);
                map.put(t, list);
            }
        }
        return map;
    }
    
    /**
     * 根据店铺号返回该店铺的商户号
     * @param shopId 店铺号
     * @return 商户号
     * @throws Exception
     */
    private static String getByShopID(String shopId) throws Exception{
        if("10001".equals(shopId)){
            return "0018888881";
        }else if("10002".equals(shopId)){
            return "0018888882";
        }else{
            throw new Exception("找不到改店铺的商户号！");
        }
    }
    
    /***
     * 设置分账信息、组装分账信息参数字符串
     * @param orderIds 订单号码
     * @param ordersAmount 订单总金额
     * @return 分账信息参数字符串
     * @throws Exception 
     * @author ZhangBing
     * @date 20140527
     * @version 2
     */
    private static String getPaymentDivDetails(List<ItemInfo> items,String ordersAmount) throws Exception{
        //分账字符串
        String divs = "";            
        String div ="";
        
        //主商户号1200000016
        String mainSid = "1200000016";    
        
        List<MyData> list = new ArrayList<MyData>();
        for(ItemInfo item : items){
            list.add(new MyData().setId(item.getId()).setShopId(item.getShopid())
                .setFxMoney(item.getFxSplitMoney()).setItemValue(item.getItemValue())) ;
        }
        
        //对得到的集合进行分组
        Map<String ,List<MyData>> map = group(list, new GroupBy<String>() {
            public String groupBy(Object obj) {
                MyData d = (MyData)obj;
                return d.getShopId();    // 分组依据为店铺ID
            }
        });
        //主商户分账总金额
        Double mainMoney = 0.0;
        Set<String> set = map.keySet();
        for(Object key : set){
            //System.out.println(key);
            String shopId = (String)key;
            //System.out.println("子商户号："+shop.getFxshopSid());
            List<MyData> datas = map.get(key);
            Double fxMoney = 0.0;
            //子商户号
            String subSid = getByShopID(shopId);
            for(MyData d : datas){
                //System.out.println("价格:"+d.getItemValue());
                //System.out.println("分账:"+d.fxMoney);
                
                //获取商品的子商户分账金额
                Double fxSplitMoney = Double.parseDouble(d.fxMoney);
                //计算主商户分账总金额
                mainMoney += Double.parseDouble(d.getItemValue()) - fxSplitMoney;
                //计算子商户分账金额
                fxMoney += fxSplitMoney;
                //System.out.println("子商户号:"+subSid+" 子商号分账总金额:"+fxMoney);
            }
            divs += subSid+":"+fxMoney+"|";
            //System.out.println(divs);
        }
        //System.out.println("主商户号:"+mainSid+" 主商号分账总金额:"+mainMoney);
        div = mainSid+":"+mainMoney+"|"+divs;
        //System.out.println(div);
        div = div.substring(0, div.length()-1);
        //System.out.println(div);
        return div;
    }
    public static void main(String[] args){
        /**
         * 模拟有一个订单，订单下有三个物品
         * ItemInfo+ordersAmount组成了一个订单信息
         */
        //订单总金额/元
        String ordersAmount = "3000";
        
        //物品1
        ItemInfo ii = new ItemInfo();
        ii.setId("1");                //订单表ID
        ii.setFxSplitMoney("100");    //分账金额，比如这个物品1价格为1000元，需要分给平台100元
        ii.setItemValue("1000");    //物品价格
        ii.setShopid("10001");        //店铺号
        //物品2
        ItemInfo ii2 = new ItemInfo();
        ii2.setId("2");
        ii2.setFxSplitMoney("300");
        ii2.setItemValue("1000");
        ii2.setShopid("10001");
        //物品3
        ItemInfo ii3 = new ItemInfo();
        ii3.setId("3");
        ii3.setFxSplitMoney("200");
        ii3.setItemValue("1000");
        ii3.setShopid("10002");
        
        List<ItemInfo> items = new ArrayList<>();
        items.add(ii);
        items.add(ii2);
        items.add(ii3);
        try {
            //得到这样的字符串：1200000016:2400.0|0018888881:400.0|0018888882:200.0
            String divDetails = getPaymentDivDetails(items, ordersAmount);
            System.out.println(divDetails);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }       
}