要使用AWS Cognito列出用户请求（ListUsersRequest），您需要使用AWS SDK提供的CognitoIdentityProviderClient。

以下是一个Java代码示例：

import com.amazonaws.auth.AWSStaticCredentialsProvider;
import com.amazonaws.auth.BasicAWSCredentials;
import com.amazonaws.regions.Regions;
import com.amazonaws.services.cognitoidp.AmazonCognitoIdentityProvider;
import com.amazonaws.services.cognitoidp.AmazonCognitoIdentityProviderClientBuilder;
import com.amazonaws.services.cognitoidp.model.ListUsersRequest;
import com.amazonaws.services.cognitoidp.model.ListUsersResult;

public class CognitoListUsersExample {

    public static void main(String[] args) {

        // 设置您的AWS凭证
        String accessKey = "your_access_key";
        String secretKey = "your_secret_key";
        BasicAWSCredentials credentials = new BasicAWSCredentials(accessKey, secretKey);

        // 创建CognitoIdentityProvider客户端
        AmazonCognitoIdentityProvider cognitoClient = AmazonCognitoIdentityProviderClientBuilder.standard()
                .withCredentials(new AWSStaticCredentialsProvider(credentials))
                .withRegion(Regions.US_EAST_1)  // 设置您的区域
                .build();

        // 创建ListUsersRequest对象
        ListUsersRequest request = new ListUsersRequest();
        request.setUserPoolId("your_user_pool_id");  // 设置您的用户池ID

        // 调用listUsers方法并处理结果
        ListUsersResult result = cognitoClient.listUsers(request);

        // 输出每个用户的用户名
        result.getUsers().forEach(user -> System.out.println("Username: " + user.getUsername()));
    }
}

请确保将代码中的"your_access_key"，"your_secret_key"和"your_user_pool_id"替换为您自己的凭证和用户池ID。

该示例将列出用户池中的所有用户，并打印出每个用户的用户名。您可以根据自己的需求修改代码，以满足特定的业务逻辑。