Java中的UDP協議常常被用來實現消息傳遞，不同于TCP協議的連接需要手動建立和關閉，UDP協議可隨時發送和接收數據。

多線程發送數據可以提高傳遞速度和效率。在使用UDP協議發送數據時，我們需要創建一個DatagramSocket對象來發送和接收數據。以下是示例代碼：

DatagramSocket socket = new DatagramSocket();
InetAddress receiverAddress = InetAddress.getByName("192.168.0.1");
int receiverPort = 5000;
String message = "Hello World";
byte[] sendData = message.getBytes();
DatagramPacket sendPacket = new DatagramPacket(sendData, sendData.length, receiverAddress, receiverPort);
socket.send(sendPacket);
socket.close();

對于多線程的UDP數據發送，可以創建多個線程來并發發送數據：

class SenderThread extends Thread {
private DatagramSocket socket;
private InetAddress receiverAddress;
private int receiverPort;
private String message;
public SenderThread(DatagramSocket socket, InetAddress receiverAddress, int receiverPort, String message) {
this.socket = socket;
this.receiverAddress = receiverAddress;
this.receiverPort = receiverPort;
this.message = message;
}
public void run() {
try {
byte[] sendData = message.getBytes();
DatagramPacket sendPacket = new DatagramPacket(sendData, sendData.length, receiverAddress, receiverPort);
socket.send(sendPacket);
} catch (Exception e) {
e.printStackTrace();
}
}
}
DatagramSocket socket = new DatagramSocket();
InetAddress receiverAddress = InetAddress.getByName("192.168.0.1");
int receiverPort = 5000;
String message1 = "Hello World 1";
String message2 = "Hello World 2";
String message3 = "Hello World 3";
SenderThread senderThread1 = new SenderThread(socket, receiverAddress, receiverPort, message1);
SenderThread senderThread2 = new SenderThread(socket, receiverAddress, receiverPort, message2);
SenderThread senderThread3 = new SenderThread(socket, receiverAddress, receiverPort, message3);
senderThread1.start();
senderThread2.start();
senderThread3.start();
socket.close();

在這個例子中，我們創建了三個SenderThread線程來并發發送三條消息。實際項目中可能需要更多的線程來發送數據。

多線程接收數據同樣可以提高效率。下面是一個示例代碼：

DatagramSocket socket = new DatagramSocket(5000);
byte[] receiveData = new byte[1024];
while (true) {
DatagramPacket receivePacket = new DatagramPacket(receiveData, receiveData.length);
socket.receive(receivePacket);
String message = new String(receivePacket.getData()).trim();
System.out.println(message);
}
socket.close();

接收數據可以在一個while循環中不停地接收。在實際使用中可能需要使用其他方法來控制多線程并發接收數據。