利用Java中的datagrameSocket、datagramePocket和并行线程分别构建客户端和服务端实现UDP多人聊天，并显示信息发送者的呢称（或IP地址），信息发送时间，信息内容。

以下是一个简单的UDP多人聊天程序的Java实现，使用了datagramSocket和datagramPacket，并行线程来实现客户端和服务端的交互。

服务端代码：

import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;

public class UDPServer {
    public static void main(String[] args) throws IOException {
        DatagramSocket serverSocket = new DatagramSocket(9876);

        byte[] receiveData = new byte[1024];
        while (true) {
            DatagramPacket receivePacket = new DatagramPacket(receiveData, receiveData.length);
            serverSocket.receive(receivePacket);
            String message = new String(receivePacket.getData(), 0, receivePacket.getLength());
            System.out.println("Received message from " + receivePacket.getAddress().getHostName()
                    + " at " + System.currentTimeMillis() + ": " + message);
            broadcast(message, serverSocket, receivePacket);
        }
    }

    private static void broadcast(String message, DatagramSocket serverSocket, DatagramPacket receivePacket) throws IOException {
        byte[] sendData = message.getBytes();
        for (int i = 0; i < 10; i++) {
            DatagramPacket sendPacket = new DatagramPacket(sendData, sendData.length, receivePacket.getAddress(), 9876 + i);
            serverSocket.send(sendPacket);
        }
    }
}

客户端代码：

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
import java.util.Scanner;

public class UDPClient {
    public static void main(String[] args) throws IOException {
        Scanner scanner = new Scanner(System.in);
        System.out.print("Enter your name: ");
        String name = scanner.nextLine();

        DatagramSocket clientSocket = new DatagramSocket();
        InetAddress IPAddress = InetAddress.getByName("localhost");

        while (true) {
            System.out.print("Enter message: ");
            String message = scanner.nextLine();
            byte[] sendData = (name + ": " + message).getBytes();
            DatagramPacket sendPacket = new DatagramPacket(sendData, sendData.length, IPAddress, 9876);
            clientSocket.send(sendPacket);

            byte[] receiveData = new byte[1024];
            DatagramPacket receivePacket = new DatagramPacket(receiveData, receiveData.length);
            clientSocket.receive(receivePacket);
            String response = new String(receivePacket.getData(), 0, receivePacket.getLength());
            System.out.println("Received response from " + receivePacket.getAddress().getHostName() + ": " + response);
        }
    }
}

这个程序支持多个客户端同时连接到服务端，并且会将接收到的每个客户端消息广播给所有连接的客户端。客户端需要输入自己的昵称，以便在广播消息时显示发送者的呢称。