我尝试在用户首次登录平台时选择。每个用户都可以在一天内多次进入该平台，我第一次选择时会遇到问题。
数据库访问类：
package poin;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.Statement;
import java.util.ArrayList;
import java.util.List;
public class DataBase {
Connection conn ;
Statement stmt;
List<Join> list = new ArrayList<Join>();
public DataBase(){
super();
}
public List<Join> getCard() throws Exception {
try{
Class.forName("com.microsoft.sqlserver.jdbc.SQLServerDriver");
conn = DriverManager.getConnection("jdbc:sqlserver://localhost:1433;user=****;password=*******;database=********");
stmt = conn.createStatement();
String sql = "SELECT [Id] ,[Last Name] ,[First Name],[Field Time] FROM [******].[dbo].[Jointur] order by [Field Time]";
ResultSet rs = stmt.executeQuery(sql);
//STEP 5: Extract data from result set
//rs.beforeFirst();
//rs.next();
//Join obj =new Join(); FAUTE CAR NOUS AVONS CR2ER UN SEUL OBJET POUR TOUTE ARRAY LIST IL FAUT ETRE A L INTERIEUR DE LA BOUCLE VOIR LA BOUCLE
while(rs.next())
{
Join obj =new Join();//
//Retrieve by column name
obj.setCardHolderId(rs.getInt("ID"));
obj.setNom(rs.getString("Last Name"));
obj.setPrenom(rs.getString("First Name"));
obj.setFieldTime(rs.getDate("Field Time"));
obj.setTimestamp(rs.getTimestamp("Fiel Time"));
list.add(obj);
}
rs.close();
stmt.close();
conn.close();
}
catch (ClassNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return list;
}
}
加入课程;此类包含在ArrayList中插入的对象类型：
package poin;
import java.sql.Timestamp;
import java.util.Date;
public class Join {
private int cardHolderId;
private String Nom;
private String Prenom;
private Date fieldTime;
private Timestamp timestamp;
public Timestamp getTimestamp() {
return timestamp;
}
public void setTimestamp(Timestamp timestamp) {
this.timestamp = timestamp;
}
public Join() {
super();
}
public int getCardHolderId() {
return cardHolderId;
}
public void setCardHolderId(int cardHolderId) {
this.cardHolderId = cardHolderId;
}
public String getNom() {
return Nom;
}
public void setNom(String nom) {
Nom = nom;
}
public String getPrenom() {
return Prenom;
}
public void setPrenom(String prenom) {
Prenom = prenom;
}
public Date getFieldTime() {
return fieldTime;
}
public void setFieldTime(Date fieldTime) {
this.fieldTime = fieldTime;
}
}
class Test：class包含main
package poin;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.GregorianCalendar;
import java.util.Date;
import java.util.Calendar;
import java.util.Iterator;
import java.util.List;
public class Test {
static Date dateDebut;
static Date dateFin;
/**
* @param args
* @throws ParseException
*/
public static void main(String[] args) throws ParseException {
String dateEntre = "2016-03-03";
String dateF = "2016-03-03";
SimpleDateFormat ft = new SimpleDateFormat ("yyyy-MM-dd");
dateDebut= ft.parse(dateEntre);
dateFin=ft.parse(dateF);
// TODO Auto-generated method stub
DataBase obj = new DataBase();
List<Join> list = new ArrayList<Join>();
List<Join> result = new ArrayList<Join>();
try {
list=obj.getCard();
//iterateur pour la liste extraite de la base de donnée
Iterator<Join> it=result.iterator();
//gregorian calendrier
GregorianCalendar cal = new GregorianCalendar();
cal.setTime(dateDebut);
//dernier element de la liste: base de donnée
Join obj2 = list.get(list.size()-1);
// dernier identifiant de la carte dans la table
int dernId = obj2.getCardHolderId();
result.add(list.get(0));
while(!cal.getTime().after(dateFin)){
for (Join j : list){
//System.out.println(cal.getTime());
//Join o = it.next();
//boolean o2 = result.add(o);
if(j.getFieldTime().compareTo(cal.getTime())==0){
//ICI LE PROBLEME (translated: HERE IS THE PROBLEM)
for (Join i : result){
if (i.getCardHolderId() != j.getCardHolderId() && i.getFieldTime() != j.getFieldTime()) result.add(j);
}
}
}
cal.add(Calendar.DAY_OF_WEEK, 1);
}
for(Join k : list){
System.out.println(k.getCardHolderId()+" "+k.getNom());
}
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
答案 0 :(得分：1)
如果您的数据存储在关系数据库中，通常最好使用SQL来获取所需的数据（而不是在代码中实现搜索逻辑）。
假设您的数据是
ID LAST_NAME FIRST_NAME FIELD_TIME
---------- --------- ---------- -------------------
1 A. A. 01.01.2016 10:20:00
2 A. A. 01.01.2016 12:22:00
3 A. A. 03.01.2016 08:50:00
4 B. B. 01.01.2016 15:08:00
要获得每个用户的第一个日志和一天，您必须从datetime列获取该日期（我使用适用于Oracle的TRUNC - 根据需要调整您的数据库）并在用户和日计算记录时间MIN。
select
LAST_NAME, FIRST_NAME, trunc(FIELD_TIME) log_day, min(FIELD_TIME) FIRST_LOG
from
log_time
group by
LAST_NAME, FIRST_NAME, trunc(FIELD_TIME)
order by
1, 2, 3;
结果与预期的一样精确，只需获取光标即可获取数据
LAST_NAME FIRST_NAME LOG_DAY FIRST_LOG
--------- ---------- ------------------- -------------------
A. A. 01.01.2016 00:00:00 01.01.2016 10:20:00
A. A. 03.01.2016 00:00:00 03.01.2016 08:50:00
B. B. 01.01.2016 00:00:00 01.01.2016 15:08:00