比如说,我一张表中取出一些数据,同一天有多条记录,我先定义了一个map集合,value是一个数组 应该怎么写
我的代码如下:while (rs.next()) {
cardnumber = rs.getString("cardnumber");
alltime = rs.getTimestamp("alltime");
System.out.println(cardnumber + "," + alltime);Map<String, Timestamp[]> map = new HashMap<String, Timestamp[]>();
String str = cardnumber;
Timestamp[] arr = { alltime };map.put(str, arr);
希望解答下,最好能基于我上面改正下
我的代码如下:while (rs.next()) {
cardnumber = rs.getString("cardnumber");
alltime = rs.getTimestamp("alltime");
System.out.println(cardnumber + "," + alltime);Map<String, Timestamp[]> map = new HashMap<String, Timestamp[]>();
String str = cardnumber;
Timestamp[] arr = { alltime };map.put(str, arr);
希望解答下,最好能基于我上面改正下
key 是用户ID value是用户记录的list 有了新记录 继续list.add
Map<String, List<String>> map = new HashMap<String, List<String>();
List<String> lst = new ArrayList<String>();
String cardnumber = "";
String alltime = "";
while (rs.next()) {
cardnumber = rs.getString("cardnumber");
alltime = rs.getTimestamp("alltime");
lst.add(alltime);
}
map.put(cardnumber, lst);
cardnumber = rs.getString("cardnumber");
alltime = rs.getTimestamp("alltime");
Map<String, List<Timestamp>> map = new HashMap<String, List<Timestamp>>();
if(map.containsKey(cardnumber)){//已经存在cardnumber key
List<Timestamp> times = map.get(cardnumber);//获取存在的key对应的集合对象
times.add(alltime);
map.put(cardnumber, times);
}else{//不存在cardnumber key
List<Timestamp> times = new ArrayList<Timestamp>();
times.add(alltime);
map.put(cardnumber, times);
}
}
这么写,请问map有什么用》?alltime还有必要保存在times 中?