Question

I have an arraylist in my metod receiveArrayLists which i want to add to a JList. How can i do this?

import java.awt.Dimension;
import java.awt.Scrollbar;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.net.InetSocketAddress;
import java.net.Socket;
import java.util.ArrayList;
import java.util.logging.Level;
import java.util.logging.Logger;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JList;
import javax.swing.JPanel;
import javax.swing.JScrollBar;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.JTextField;

public class GUI implements Runnable {

private Server server;
private JFrame frame = new JFrame();
private JTextField jtf = new JTextField();
private JList jl = new JList();
private JTextArea jl1 = new JTextArea();
private JScrollPane pane = new JScrollPane(jl);
private Socket socket;
private DataInputStream dis;
private ObjectInputStream ois = null;
private DataOutputStream dos;

public GUI() {

    socket = new Socket();
    InetSocketAddress ipPort = new InetSocketAddress("127.0.0.1", 4444);
    try {
        socket.connect(ipPort);
        dis = new DataInputStream(socket.getInputStream());
        dos = new DataOutputStream(socket.getOutputStream());
    } catch (Exception e) {
    }
    new Thread(this).start();


    frame.getContentPane().setLayout(null);
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.setBounds(50, 300, 420, 400);
    frame.setResizable(false);
    frame.setVisible(true);
    pane.add(jl);
    pane.add(jl1);
    jl1.setEditable(false);
    jtf.setBounds(50, 40, 150, 40);
    jl.setBounds(50, 90, 150, 200);
    jl1.setBounds(210, 90, 150, 200);


    jtf.addKeyListener(new KeyListener() {

        public void keyTyped(KeyEvent e) {
        }

        public void keyPressed(KeyEvent e) {
        }

        public void keyReleased(KeyEvent e) {
            if (dos != null) {
                if(jtf.getText().length() >0){
                try {
                    dos.writeUTF(jtf.getText());
                } catch (IOException ex) {
                    Logger.getLogger(GUI.class.getName()).log(Level.SEVERE, null, ex);
                }
                }else{
                    jl1.setText("");
                }
            }

        }
    });
    frame.add(jtf);
    frame.add(jl);
    frame.add(jl1);

    frame.add(pane);
}

public void run() {
    String fromServer;
    try {
        while ((fromServer = dis.readUTF()) != null) {
            if (fromServer.equals("read")) {
                receiveArrayList();
            }
        }
    } catch (Exception e) {

    }
}

Here is my metod, as you can see, i try to use append which obviously wont work to add an arraylist to a JList

public void receiveArrayList() {

    try {
        jl1.setText("");
        ois = new ObjectInputStream(socket.getInputStream());
        @SuppressWarnings("unchecked")
        ArrayList<String> a = (ArrayList<String>) (ois.readObject());
        for (int i = 0; i < a.size(); i++) {
            jl.append(a.get(i) + " \n");
        }
        dis = new DataInputStream(socket.getInputStream());
    } catch (ClassNotFoundException ex) {
        System.out.println(ex);
    } catch (IOException ex) {
        System.out.println(ex);
    }
}

public static void main(String[] args) {
    GUI g = new GUI();

}
}

Answer 1

The simplest is to create a DefaultListModel object, iterate through the ArrayList in a for or foreach loop and add the items to the model via its addElement(...) method. Then set the JList’s model to your model.

More involved but satisfying is to create your own ListModel by extending AbstractListModel using your ArrayList as the model’s nucleus.