Java作为一门强大的编程语言，被广泛运用在Web开发中。Node.js则是一种轻量级的JavaScript运行环境，可用于构建高效的Web应用程序。

在现代Web应用程序中，Java和Node.js可以很容易地彼此通信以实现某些业务需求。下面我们将介绍一些通信的方法。

1. 使用HTTP协议通信

// Java端
public static void main(String[] args) {
  HttpClient httpClient = HttpClientBuilder.create().build();
  HttpPost httpPost = new HttpPost("http://localhost:3000/api");
  StringEntity params = new StringEntity("{\"data\":\"hello from Java\"}");
  httpPost.setEntity(params);
  httpPost.setHeader("Content-type", "application/json");
  HttpResponse response = httpClient.execute(httpPost);
  System.out.println(response.getStatusLine().getStatusCode()); 
}

// Node.js端
const http = require('http');

const server = http.createServer((req, res) => {
  if(req.url === '/api' && req.method === 'POST') {
    let body = '';
    req.on('data', chunk => {
      body += chunk.toString();
    });
    req.on('end', () => {
      console.log(JSON.parse(body)); // { data: 'hello from Java' }
      res.statusCode = 200;
      res.setHeader('Content-Type', 'text/plain');
      res.end('Hello from Node.js\n');
    });
  }
});

server.listen(3000, () => {
  console.log('Listening on http://localhost:3000');
});

2. 使用Socket通信

// Java端
public static void main(String[] args) throws Exception {
  Socket socket = new Socket("localhost", 3000);
  PrintWriter out = new PrintWriter(socket.getOutputStream(), true);
  out.println("hello from Java");
  out.close();
  socket.close();
}

// Node.js端
const server = require('net').createServer();

server.on('connection', conn => {
  conn.on('data', data => {
    console.log(data.toString()); // hello from Java
    conn.end();
  });
});

server.listen(3000, () => {
  console.log('Listening on http://localhost:3000');
});

通过HTTP协议或Socket通信，Java和Node.js可以互相传递数据以及执行相应的操作。在实际应用中，具体选择哪种通信方式需要根据具体需求综合考虑。