java - Java ArrayList获取元素的方法

Question

我有一个基本问题。我有这个 ArrayList:

@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;
    }
}

我尝试使用这段 Java 代码获取元素:

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));

但我在 Netbeans 中遇到错误。你能告诉我从 ArrayList 中获取元素的正确方法是什么吗？

祝福

Answer 1

使用 for-each 循环这是优化方式...

for(userdata obj : dataList){

   System.out.println("User ID :: " + obj.userid);
   System.out.println("Group ID :: " + obj.groupid);
   .
   .
   .

}

使用for循环

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);
       .
       .
       .

    }