java如何将从数据库提取的对象添加到arraylist？

Question

我编写了一个简单的程序，从数据库中提取一些数据，数据库表中的每一行都是用一个普通构造函数创建的对象来构造的，然后我使用。add（）方法。 我的问题是，当我输出我的arraylist包含的内容时，我发现所有的案例都只包含数据库中的最后一行！！我尝试在添加到arraylist时打印，发现每次添加新对象时，它都会出现在arraylist的新旧大小写中，因此最后一个对象（代表数据库表的最后一行）会出现在所有arraylist中！ 有什么帮助吗

以下是我的两门课： 客户端。java

public class Client {
    public static String nom, prenom, adrs;
    private static int id, maxcredit, totalpaye, totalnonpaye;

    //i want data to be stored in this arraylist
    public static ArrayList<ClientInfo> clients =  new ArrayList();

public Client(){    
    connectDB();//connecting to the database
    getClients();//storing the data from the database to arraylist!!
}

private static Connection conn = null;
private static Statement stmt = null;
private static ResultSet rs = null;

private static final String Conn_string = "jdbc:mysql://localhost/carnetcredit";



//Connect to DB:
public static void connectDB(){
    try{
        conn = DriverManager.getConnection(Conn_string, "root", "");
    }catch(SQLException e){
        System.err.println(e);
    }
}

//Get all clients list:
public static void getClients(){
    try{

        stmt = conn.createStatement(ResultSet.TYPE_SCROLL_SENSITIVE, ResultSet.CONCUR_READ_ONLY);
        rs = stmt.executeQuery("select * from client");

        System.out.println("Table Client : ");

        while (rs.next()){

            //getting data from database to simpte variables
            id = rs.getInt("idclient");
            nom = rs.getString(2);
            prenom = rs.getString(3);
            adrs = rs.getString(4);
            maxcredit = rs.getInt(5);
            totalpaye = rs.getInt(6);
            totalnonpaye = rs.getInt(7);

            //creating an object using the data extracted from the database
            ClientInfo client = new ClientInfo(id,nom,prenom,adrs,maxcredit,totalpaye,totalnonpaye);

            //adding the object to the arraylist
            clients.add(client);

    }

    }catch(SQLException e){
        System.err.println(e);
    }

}


//::::::::::::::::::::::::::::::::::::::::::::::::::: Main Method :::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
public static void main(String[] args) {

    conn = null;
    stmt = null;
    rs = null;


    ClientInfo client = new ClientInfo();
    new Client();
    int i = 0;
    while (i<clients.size()){
        client = clients.get(i);
        System.out.println("id : "+ client.id +" - nom : "+client.nom+" - prenom : "+client.prenom+" - adresse : "+client.adrs+
                " - maxcredit : "+client.maxcredit+" - total payé : "+client.totalpaye+" - total non payé : "+client.totalnonpaye);
        i++;
    }
}
//:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::

}

ClientInfo。java

public class ClientInfo {

    public  String nom, prenom, adrs;
    public  int id, maxcredit, totalpaye, totalnonpaye;


public ClientInfo(){
    id = 0;
    nom = prenom = adrs = "";
    maxcredit = totalpaye = totalnonpaye = 0;
}

public ClientInfo(int id, String nom, String prenom, String adrs, int maxcredit, int totalpaye,int totalnonpaye){
    this.id = id;
    this.nom = nom;
    this.prenom = prenom;
    this.adrs = adrs ;
    this.maxcredit = maxcredit ;
    this.totalpaye = totalpaye ;
    this.totalnonpaye = totalnonpaye;

}


  }

谢谢大家

Answer 1

每当我看到

只包含数据库中的最后一行

我自动知道这是由静态变量引起的

改变

public static String nom, prenom, adrs;
private static int id, maxcredit, totalpaye, totalnonpaye;

非静态