集合分组Map

[月似人伤]

List<LedgerInfo> result = new ArrayList<LedgerInfo>();
if (null == list || list.size() == 0)
{
return result;
}
Map<String, String> map = new HashMap<String, String>();
Map<String, List<LedgerInfo>> listMap = new LinkedHashMap<String, List<LedgerInfo>>();
List<LedgerInfo> modelList = null;
for (LedgerInfo ledgerInfo : list)
{
String accOperId = ledgerInfo.getAccOperId(); //accOperId
String dealerID = ledgerInfo.getDealerID(); //门店ID
String temp = accOperId + "_" + dealerID;
if (map.get(temp) == null)
{
modelList = new ArrayList<LedgerInfo>();
map.put(temp, temp);
}
else
{
modelList = (List<LedgerInfo>) listMap.get(temp);
}
modelList.add(ledgerInfo);
listMap.put(temp, modelList);
}




Map<String, String> map = new HashMap<String, String>();
  map.put("1", "value1");
  map.put("2", "value2");
  map.put("3", "value3");
  
  //第一种：普遍使用，二次取值
  System.out.println("通过Map.keySet遍历key和value：");
  for (String key : map.keySet()) {
   System.out.println("key= "+ key + " and value= " + map.get(key));
  }
  
  //第二种
  System.out.println("通过Map.entrySet使用iterator遍历key和value：");
  Iterator<Map.Entry<String, String>> it = map.entrySet().iterator();
  while (it.hasNext()) {
   Map.Entry<String, String> entry = it.next();
   System.out.println("key= " + entry.getKey() + " and value= " + entry.getValue());
  }
  
  //第三种：推荐，尤其是容量大时
  System.out.println("通过Map.entrySet遍历key和value");
  for (Map.Entry<String, String> entry : map.entrySet()) {
   System.out.println("key= " + entry.getKey() + " and value= " + entry.getValue());
  }
  //第四种
  System.out.println("通过Map.values()遍历所有的value，但不能遍历key");
  for (String v : map.values()) {
   System.out.println("value= " + v);
  }
 }