AWS Elastic Beanstalk将应用程序的日志文件存储在Amazon CloudWatch中。Java应用程序的默认CloudWatch日志位置取决于应用程序的日志配置。

以下是一个使用Java代码示例，获取默认CloudWatch日志位置的方法：

import com.amazonaws.auth.DefaultAWSCredentialsProviderChain;
import com.amazonaws.services.elasticbeanstalk.AWSElasticBeanstalk;
import com.amazonaws.services.elasticbeanstalk.AWSElasticBeanstalkClientBuilder;
import com.amazonaws.services.elasticbeanstalk.model.DescribeEnvironmentsRequest;
import com.amazonaws.services.elasticbeanstalk.model.DescribeEnvironmentsResult;
import com.amazonaws.services.elasticbeanstalk.model.EnvironmentDescription;

public class Main {
    public static void main(String[] args) {
        // 创建Elastic Beanstalk客户端
        AWSElasticBeanstalk elasticBeanstalkClient = AWSElasticBeanstalkClientBuilder.defaultClient();

        // 构建DescribeEnvironmentsRequest对象
        DescribeEnvironmentsRequest request = new DescribeEnvironmentsRequest();
        request.setEnvironmentIds("your-environment-id"); // 替换为实际的环境ID

        // 发送请求并获取DescribeEnvironmentsResult对象
        DescribeEnvironmentsResult result = elasticBeanstalkClient.describeEnvironments(request);

        // 获取EnvironmentDescription对象
        EnvironmentDescription environment = result.getEnvironments().get(0); // 假设只有一个环境

        // 获取默认CloudWatch日志位置
        String logStream = environment.getEndpointURL() + "/var/log/web.stdout.log";

        // 打印日志位置
        System.out.println("Default CloudWatch log location: " + logStream);
    }
}

在示例代码中，我们使用AWS SDK for Java创建了Elastic Beanstalk客户端。然后，我们构建了一个DescribeEnvironmentsRequest对象，并设置要描述的环境ID。发送请求后，我们从DescribeEnvironmentsResult对象中获取EnvironmentDescription对象。最后，我们使用EnvironmentDescription对象的getEndpointURL()方法获取默认CloudWatch日志位置，并打印出来。

请注意，您需要将"your-environment-id"替换为实际的环境ID。