java - Java ArrayList から要素を取得する方法

Question

基本的な質問があります。私はこのArrayListを持っています:

@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;
    }
}

このJavaコードを使用して要素を取得しようとしました:

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));

しかし、Netbeans でエラーが発生します。ArrayList から要素を取得する適切な方法を教えてください。

幸運をお祈りしています

Answer 1

使用するfor-each loop this is optimize way...

for(userdata obj : dataList){

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

}

for ループの使用

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);
       .
       .
       .

    }

Answer 2

ArrayList<userdata> dataList = new ArrayList<>();
dataList.add(new userdata(...)); // The ... is for all your params
userdata data = dataList.get(0); // This gets the first element of the list, the one we just added
System.out.println(data.getCity()); // This will print the String called city

補足として、userdata は UserData である必要があります。定義するクラスの最初の文字に大文字を使用するのは Java の規則です。

編集:

あなたが今何をしようとしているのか分かります。挿入を次のように変更したいと思うでしょう:

for (userdata data : dataList) {
    ps.setInt(1, data.getUserid());
    ps.setInt(2, data.getGroupid());
    ...
}

また、新しいアイテムの挿入と古いアイテムの更新を実行する必要があります。

Answer 3

ps.setInt(1, dataList.get(i).getUserId());

Answer 4

これを試して

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
}

基本的に、dataList.get(index) を使用してリストからユーザーデータ項目を取得し、ユーザーデータのインスタンスからフィールドを引き出す必要があります。

みたいな

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
}

Answer 5

オブジェクト dataList には、タイプ userData のオブジェクトが含まれています（ちなみに、UserData である必要があります）。

を呼び出すとdataList.get(something)、その何かは整数値である必要があり、getメソッドはその位置にあるオブジェクトを取得します。

PreparedStatement をリストの最初のオブジェクトで埋めたい場合は、次のようにします。

UserData user = dataList.get(0);
ps.setInt(1, user.getUserId())
...

すべてのユーザーに対して同じことをしたい場合：

for(userdata obj : dataList){

    ps.setInt(1, obj.userid);
    ...

    //do something with PS for this object.
}

Answer 6

リスト内のすべてのアイテムを更新しようとしている場合は、各アイテムをループして個別に実行する必要があります。

 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();
    }

}

この場合、2 つにする理由がないため、finally ブロックも統合しました。