如何从Java ArrayList获取元素
我有一个基本问题。我有一个ArrayList：如何从Java ArrayList获取元素,java,Java,我有一个基本问题。我有一个ArrayList： @Named("AccountProfileController") @ViewScoped public class AccountProfile implements Serializable { @Resource(name = "jdbc/Oracle") private DataSource ds; private int id; // Constructor public AccountPro
@Named("AccountProfileController")
@ViewScoped
public class AccountProfile implements Serializable
{
@Resource(name = "jdbc/Oracle")
private DataSource ds;
private int id;
// Constructor
public AccountProfile()
{
// get the ID value
try
{
this.id = Integer.parseInt((String) FacesContext.getCurrentInstance().getExternalContext().getRequestParameterMap().get("id"));
}
catch (Exception e)
{
this.id = 0;
}
}
// Create List to store user data
public ArrayList<userdata> dataList = new ArrayList<>();
public class userdata
{
int userid;
int groupid;
String specialnumber;
String username;
String passwd;
Date datetochangepasswd;
String address;
String stateregion;
String country;
String userstatus;
String telephone;
Date dateuseradded;
Date userexpiredate;
Date dateuserlocked;
String city;
String email;
String description;
public userdata(int userid, int groupid, String specialnumber, String username, String passwd, Date datetochangepasswd,
String address, String stateregion, String country, String userstatus, String telephone, Date dateuseradded,
Date userexpiredate, Date dateuserlocked, String city, String email, String description)
{
this.userid = userid;
this.groupid = groupid;
this.specialnumber = specialnumber;
this.username = username;
this.passwd = passwd;
this.datetochangepasswd = datetochangepasswd;
this.address = address;
this.stateregion = stateregion;
this.country = country;
this.userstatus = userstatus;
this.telephone = telephone;
this.dateuseradded = dateuseradded;
this.userexpiredate = userexpiredate;
this.dateuserlocked = dateuserlocked;
this.city = city;
this.email = email;
this.description = description;
}
public String getAddress()
{
return address;
}
public void setAddress(String address)
{
this.address = address;
}
public String getCity()
{
return city;
}
public void setCity(String city)
{
this.city = city;
}
public String getCountry()
{
return country;
}
public void setCountry(String country)
{
this.country = country;
}
public Date getDatetochangepasswd()
{
return datetochangepasswd;
}
public void setDatetochangepasswd(Date datetochangepasswd)
{
this.datetochangepasswd = datetochangepasswd;
}
public Date getDateuseradded()
{
return dateuseradded;
}
public void setDateuseradded(Date dateuseradded)
{
this.dateuseradded = dateuseradded;
}
public Date getDateuserlocked()
{
return dateuserlocked;
}
public void setDateuserlocked(Date dateuserlocked)
{
this.dateuserlocked = dateuserlocked;
}
public String getDescription()
{
return description;
}
public void setDescription(String description)
{
this.description = description;
}
public String getEmail()
{
return email;
}
public void setEmail(String email)
{
this.email = email;
}
public int getGroupid()
{
return groupid;
}
public void setGroupid(int groupid)
{
this.groupid = groupid;
}
public String getPasswd()
{
return passwd;
}
public void setPasswd(String passwd)
{
this.passwd = passwd;
}
public String getSpecialnumber()
{
return specialnumber;
}
public void setSpecialnumber(String specialnumber)
{
this.specialnumber = specialnumber;
}
public String getStateregion()
{
return stateregion;
}
public void setStateregion(String stateregion)
{
this.stateregion = stateregion;
}
public String getTelephone()
{
return telephone;
}
public void setTelephone(String telephone)
{
this.telephone = telephone;
}
public Date getUserexpiredate()
{
return userexpiredate;
}
public void setUserexpiredate(Date userexpiredate)
{
this.userexpiredate = userexpiredate;
}
public int getUserid()
{
return userid;
}
public void setUserid(int userid)
{
this.userid = userid;
}
public String getUsername()
{
return username;
}
public void setUsername(String username)
{
this.username = username;
}
public String getUserstatus()
{
return userstatus;
}
public void setUserstatus(String userstatus)
{
this.userstatus = userstatus;
}
}
// Getter for the data list
public ArrayList<userdata> getuserdata()
{
return dataList;
}
@PostConstruct
public void initData() throws SQLException
{
// settingsMap = new HashMap<String, String>();
if (ds == null)
{
throw new SQLException("Can't get data source");
}
// Initialize a connection to Oracle
Connection conn = ds.getConnection();
if (conn == null)
{
throw new SQLException("Can't get database connection");
}
// With SQL statement get all settings and values
PreparedStatement ps = conn.prepareStatement("SELECT * from USERS where USERID = ?");
ps.setInt(1, id);
try
{
//get data from database
ResultSet result = ps.executeQuery();
while (result.next())
{
// Put the the data from Oracle into Array List
dataList.add(new userdata(result.getInt("USERID"),
result.getInt("GROUPID"),
result.getString("SPECIALNUMBER"),
result.getString("USERNAME"),
result.getString("PASSWD"),
toDate(result.getString("DATETOCHANGEPASSWD")),
result.getString("ADDRESS"),
result.getString("STATEREGION"),
result.getString("COUNTRY"),
result.getString("USERSTATUS"),
result.getString("TELEPHONE"),
toDate(result.getString("DATEUSERADDED")),
toDate(result.getString("USEREXPIREDATE")),
toDate(result.getString("DATEUSERLOCKED")),
result.getString("CITY"),
result.getString("EMAIL"),
result.getString("DESCRIPTION")));
}
}
finally
{
ps.close();
conn.close();
}
}
// Call Crypto library for password convert into SHA hash
@Inject
@OSGiService(dynamic = true, waitTimeout = 5)
transient CryptoSHA SHA;
// Convert Password String into SHA hash
public String passwdConvert(String password) throws NoSuchAlgorithmException
{
return SHA.ShaEncryptHash(password);
}
// Insert the data into Oracle
public void saveData() throws SQLException, java.text.ParseException, NoSuchAlgorithmException
{
String SqlStatement = null;
if (ds == null)
{
throw new SQLException();
}
Connection conn = ds.getConnection();
if (conn == null)
{
throw new SQLException();
}
PreparedStatement ps = null;
try
{
conn.setAutoCommit(false);
boolean committed = false;
try
{ /*
* insert into Oracle the default system(Linux) time
*/
SqlStatement = "UPDATE USERS "
+ "SET "
+ "USERID = ?, "
+ "GROUPID = ?, "
+ "SPECIALNUMBER = ?, "
+ "USERNAME = ?, "
+ "PASSWD = ?, "
+ "DATETOCHANGEPASSWD = ?, "
+ "ADDRESS = ?, "
+ "STATEREGION = ?, "
+ "COUNTRY = ?, "
+ "USERSTATUS = ?, "
+ "TELEPHONE = ?, "
+ "DATEUSERADDED = ?, "
+ "USEREXPIREDATE = ?, "
+ "DATEUSERLOCKED = ?, "
+ "CITY = ?, "
+ "EMAIL = ?, "
+ "DESCRIPTION = ? "
+ "WHERE USERID = " + id;
ps = conn.prepareStatement(SqlStatement);
ps.setInt(1, dataList.get(userid));
ps.setInt(2, dataList.get(groupid));
ps.setString(3, dataList.get(specialnumber));
ps.setString(4, dataList.get(username));
ps.setString(5, passwdConvert(dataList.get(passwd)));
ps.setDate(6, toDate(dataList.get(datetochangepasswd)));
ps.setString(7, dataList.get(address));
ps.setString(8, dataList.get(stateregion));
ps.setString(9, dataList.get(country));
ps.setString(10, dataList.get(userstatus));
ps.setString(11, dataList.get(telephone));
ps.setDate(12, toDate(dataList.get(dateuseradded)));
ps.setDate(13, toDate(dataList.get(userexpiredate)));
ps.setDate(14, toDate(dataList.get(dateuserlocked)));
ps.setString(15, dataList.get(city));
ps.setString(16, dataList.get(email));
ps.setString(17, dataList.get(description));
ps.executeUpdate();
conn.commit();
committed = true;
}
finally
{
if (!committed)
{
conn.rollback();
}
}
}
finally
{
/*
* Release the resources
*/
ps.close();
conn.close();
}
}
//!!!! http://stackoverflow.com/questions/11135675/unparseable-date-30-jun-12
// Convert the Date format
public Date toDate(String s)
{
Date d = null;
if (s == null || s.trim().isEmpty())
{
return d;
}
try
{
d = Date.valueOf(s);
}
catch (Exception x)
{
x.printStackTrace();
}
return d;
}
}
最好的祝愿对每个循环使用
，这是一种优化方式…for(userdata obj : dataList){
System.out.println("User ID :: " + obj.userid);
System.out.println("Group ID :: " + obj.groupid);
.
.
.
}
for(int i =0;i<datalist.size();i++){
userdate obj=datalist.get(i);
System.out.println("User ID :: " + obj.userid);
System.out.println("Group ID :: " + obj.groupid);
.
.
.
}
for（int i=0；i
您还需要为新项目执行插入，并为旧项目执行更新。您的对象数据列表包含userData类型的对象（顺便说一句，应该是userData）
ps.setInt(1, dataList.get(i).getUserId());
调用dataList.get（something）
时，something应该是一个整数值，get
方法检索该位置的对象
如果要用列表中的第一个对象填充PreparedStatement，您需要做的是：
UserData user = dataList.get(0);
ps.setInt(1, user.getUserId())
...
如果要对每个用户执行相同的操作：
for(userdata obj : dataList){
ps.setInt(1, obj.userid);
...
//do something with PS for this object.
}
试试这个
for(userdata datum : dataList)
{ //for each userdata instance in dataList collection
ps.setInt(1, datum.userid); //ps.setInt(1, datum.getUserid());
ps.setInt(2, datum.groupid);
ps.setString(3, datum.specialnumber);
//... you get the idea
}
基本上，您需要使用dataList.get（index）从列表中获取userdata项，然后从userdata实例中提取字段
有点像这样
for(int i = 0; i < dataList.size(); i++)
{
ps.setInt(1, dataList.get(i).getUserid()); //ps.setInt(1, datum.getUserid());
ps.setInt(2, dataList.get(i).getGroupId());
ps.setString(3, dataList.get(i).specialnumber);
//... you get the idea
}
for（int i=0；i
如果您试图更新列表中的每个项目，则需要循环遍历每个项目并单独执行它们
public void saveData() throws SQLException, java.text.ParseException, NoSuchAlgorithmException {
String SqlStatement = null;
if (ds == null) {
throw new SQLException();
}
Connection conn = ds.getConnection();
if (conn == null) {
throw new SQLException();
}
PreparedStatement ps = null;
try {
conn.setAutoCommit(false);
boolean committed = false;
//removed the userid as that is used in the where to determine what record to update
//so it will be the same
SqlStatement = "UPDATE USERS "
+ "SET "
+ "GROUPID = ?, "
+ "SPECIALNUMBER = ?, "
+ "USERNAME = ?, "
+ "PASSWD = ?, "
+ "DATETOCHANGEPASSWD = ?, "
+ "ADDRESS = ?, "
+ "STATEREGION = ?, "
+ "COUNTRY = ?, "
+ "USERSTATUS = ?, "
+ "TELEPHONE = ?, "
+ "DATEUSERADDED = ?, "
+ "USEREXPIREDATE = ?, "
+ "DATEUSERLOCKED = ?, "
+ "CITY = ?, "
+ "EMAIL = ?, "
+ "DESCRIPTION = ? "
+ "WHERE USERID = " + ?; //also changed this to be a parameter
ps = conn.prepareStatement(SqlStatement);
for (userdata data: datalist) {
ps.setInt(1, dataList.getGroupid());
ps.setString(2, dataList.getSpecialnumber());
...
//continue setting the others variables
//the last on will be the userid in the where clause
ps.setInt(17, dataList.getUserId());
//execute the update
ps.executeUpdate();
}
//now we commit since they have all ran. We want an all or nothing update
//meaning if one fails, nothing is updated
conn.commit();
committed = true;
}
finally
{
if (!committed){
conn.rollback();
}
ps.close();
conn.close();
}
}
我还整合了finally块，因为在这种情况下没有理由有两个。谁说Java是冗长的？谁说这是使用Java的好方法？我是Java新手。你能告诉我问题出在哪里以及如何解决吗？什么是ps
？一个ArrayList
？我想你可能需要指定你的目标我只想使用getter方法添加，因为这取决于他在列表中的迭代位置，它可能无法按您的方式工作。
for(userdata datum : dataList)
{ //for each userdata instance in dataList collection
ps.setInt(1, datum.userid); //ps.setInt(1, datum.getUserid());
ps.setInt(2, datum.groupid);
ps.setString(3, datum.specialnumber);
//... you get the idea
}
for(int i = 0; i < dataList.size(); i++)
{
ps.setInt(1, dataList.get(i).getUserid()); //ps.setInt(1, datum.getUserid());
ps.setInt(2, dataList.get(i).getGroupId());
ps.setString(3, dataList.get(i).specialnumber);
//... you get the idea
}
public void saveData() throws SQLException, java.text.ParseException, NoSuchAlgorithmException {
String SqlStatement = null;
if (ds == null) {
throw new SQLException();
}
Connection conn = ds.getConnection();
if (conn == null) {
throw new SQLException();
}
PreparedStatement ps = null;
try {
conn.setAutoCommit(false);
boolean committed = false;
//removed the userid as that is used in the where to determine what record to update
//so it will be the same
SqlStatement = "UPDATE USERS "
+ "SET "
+ "GROUPID = ?, "
+ "SPECIALNUMBER = ?, "
+ "USERNAME = ?, "
+ "PASSWD = ?, "
+ "DATETOCHANGEPASSWD = ?, "
+ "ADDRESS = ?, "
+ "STATEREGION = ?, "
+ "COUNTRY = ?, "
+ "USERSTATUS = ?, "
+ "TELEPHONE = ?, "
+ "DATEUSERADDED = ?, "
+ "USEREXPIREDATE = ?, "
+ "DATEUSERLOCKED = ?, "
+ "CITY = ?, "
+ "EMAIL = ?, "
+ "DESCRIPTION = ? "
+ "WHERE USERID = " + ?; //also changed this to be a parameter
ps = conn.prepareStatement(SqlStatement);
for (userdata data: datalist) {
ps.setInt(1, dataList.getGroupid());
ps.setString(2, dataList.getSpecialnumber());
...
//continue setting the others variables
//the last on will be the userid in the where clause
ps.setInt(17, dataList.getUserId());
//execute the update
ps.executeUpdate();
}
//now we commit since they have all ran. We want an all or nothing update
//meaning if one fails, nothing is updated
conn.commit();
committed = true;
}
finally
{
if (!committed){
conn.rollback();
}
ps.close();
conn.close();
}
}