import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.Statement;

public class JdbcAggregateExample {
    public static void main(String[] args) {
        String url = "jdbc:mysql://localhost:3306/your_database";
        String user = "your_username";
        String password = "your_password";

        try (Connection conn = DriverManager.getConnection(url, user, password);
             Statement stmt = conn.createStatement();
             ResultSet rs = stmt.executeQuery("SELECT AVG(salary) FROM employees")) {

            if (rs.next()) {
                System.out.println("Average Salary: " + rs.getDouble(1));
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

<select id="queryMaxSalary" resultType="int">
    SELECT MAX(salary) FROM employees
</select>

public class MyBatisAggregateExample {
    public int queryMaxSalary() {
        return sqlSession.selectOne("queryMaxSalary");
    }
}

import org.apache.spark.sql.Dataset;
import org.apache.spark.sql.Encoders;
import org.apache.spark.sql.SparkSession;
import org.apache.spark.sql.expressions.Aggregator;

public class SparkAggregateExample {
    public static void main(String[] args) {
        SparkSession spark = SparkSession.builder().appName("UDAF Example").getOrCreate();

        Dataset<Integer> ds = spark.createDataset(Arrays.asList(1, 2, 3, 4), Encoders.INT());

        Aggregator<Integer, Integer, Integer> sumAggregator = new Aggregator<Integer, Integer, Integer>() {
            @Override
            public Integer zero() {
                return 0;
            }

            @Override
            public Integer reduce(Integer buffer, Integer element) {
                return buffer + element;
            }

            @Override
            public Integer merge(Integer b1, Integer b2) {
                return b1 + b2;
            }

            @Override
            public Integer finish(Integer reduction) {
                return reduction;
            }

            @Override
            public Encoder<Integer> bufferEncoder() {
                return Encoders.INT();
            }

            @Override
            public Encoder<Integer> outputEncoder() {
                return Encoders.INT();
            }
        };

        Dataset<Integer> result = ds.select(sumAggregator.toColumn().name("sum"));
        result.show();
    }
}

import org.elasticsearch.action.search.SearchRequest;
import org.elasticsearch.action.search.SearchResponse;
import org.elasticsearch.client.RequestOptions;
import org.elasticsearch.client.RestHighLevelClient;
import org.elasticsearch.index.query.QueryBuilders;
import org.elasticsearch.search.aggregations.AggregationBuilders;
import org.elasticsearch.search.aggregations.metrics.sum.Sum;

public class ElasticsearchAggregateExample {
    public void executeAggregation(RestHighLevelClient client) throws IOException {
        SearchRequest searchRequest = new SearchRequest("your_index");
        searchRequest.source(new SearchSourceBuilder()
                .query(QueryBuilders.matchAllQuery())
                .aggregation(AggregationBuilders.sum("total_sales").field("sales")));

        SearchResponse searchResponse = client.search(searchRequest, RequestOptions.DEFAULT);
        Sum totalSales = searchResponse.getAggregations().get("total_sales");
        System.out.println("Total Sales: " + totalSales.getValue());
    }
}