java调用PublishMessage

我认为你指的是调用AWS IoT Core的Publish方法来发送消息。下面是一个简单的Java代码示例：

import com.amazonaws.services.iot.client.AWSIotException;
import com.amazonaws.services.iot.client.AWSIotMqttClient;
import com.amazonaws.services.iot.client.AWSIotQos;
import com.amazonaws.services.iot.client.AWSIotTopic;

public class PublishMessage {

    private static final String clientEndpoint = "<your-iot-endpoint>";
    private static final String clientId = "<your-iot-client-id>";
    private static final String topicName = "<your-iot-topic-name>";
    private static final AWSIotQos qos = AWSIotQos.QOS0; // choose the quality of service

    public static void main(String[] args) {

        AWSIotMqttClient client = new AWSIotMqttClient(clientEndpoint, clientId);

        try {
            client.connect(); // connect to IoT Core

            AWSIotTopic topic = new AWSIotTopic(topicName, qos, client); // create a new topic object
            String payload = "Hello from Java!"; // the message you want to send
            topic.publish(payload); // publish the message to the topic

            System.out.println("Message published successfully!");

        } catch (AWSIotException e) {
            System.out.println("Error publishing message: " + e.getMessage());
            e.printStackTrace();
        } finally {
            client.disconnect(); // disconnect from IoT Core
        }
    }
}

在这个示例中，我们首先创建了一个`AWSIotMqttClient`对象并连接到IoT Core。然后，我们创建了一个`AWSIotTopic`对象来表示我们要发布的主题，并调用`publish`方法将消息发送到该主题。最后，我们断开了与IoT Core的连接。

请注意，这只是一个简单的示例，需要根据您的实际需求进行修改。例如，您可能需要更改MQTT客户端的连接设置，或者使用不同的质量服务等。