import java.util.*;
import java.util.stream.Collectors;

public class MapReduceExample {
    public static void main(String[] args) {
        List<Integer> numbers = Arrays.asList(1, 2, 3, 4, 5, 6, 7, 8, 9, 10);

        // Map phase: Multiply each number by 2
        List<Integer> mappedNumbers = numbers.stream()
                .map(number -> number * 2)
                .collect(Collectors.toList());

        // Reduce phase: Sum all the mapped numbers
        int sum = mappedNumbers.stream()
                .reduce(0, Integer::sum);

        System.out.println("Sum: " + sum);
    }
}

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
@RequestMapping("/hello")
public class HelloMicroservice {

    @GetMapping
    public String sayHello() {
        return "Hello from the microservice!";
    }

    public static void main(String[] args) {
        SpringApplication.run(HelloMicroservice.class, args);
    }
}

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

public class DataWarehouseExample {
    public static void main(String[] args) {
        try (Connection connection = DriverManager.getConnection("jdbc:mysql://localhost:3306/data_warehouse", "username", "password")) {
            Statement statement = connection.createStatement();

            // Create dimension tables
            statement.executeUpdate("CREATE TABLE dim_customer (customer_id INT PRIMARY KEY, name VARCHAR(100))");
            statement.executeUpdate("CREATE TABLE dim_product (product_id INT PRIMARY KEY, name VARCHAR(100))");

            // Create fact table
            statement.executeUpdate("CREATE TABLE fact_sales (sale_id INT PRIMARY KEY, customer_id INT, product_id INT, quantity INT, amount DECIMAL(10, 2))");

            System.out.println("Data warehouse tables created successfully.");
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

public class DataLakeExample {
    public static void main(String[] args) {
        Configuration conf = new Configuration();
        conf.set("fs.defaultFS", "hdfs://localhost:9000");

        try {
            FileSystem fs = FileSystem.get(conf);

            // Write data to the data lake
            Path filePath = new Path("/data/sample.txt");
            String data = "Hello, Data Lake!";
            fs.create(filePath).write(data.getBytes());

            // Read data from the data lake
            BufferedReader reader = new BufferedReader(new InputStreamReader(fs.open(filePath)));
            String line;
            while ((line = reader.readLine()) != null) {
                System.out.println(line);
            }

            reader.close();
            fs.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.Mapper;
import org.apache.hadoop.mapreduce.Reducer;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;

import java.io.IOException;
import java.util.StringTokenizer;

public class MapReduceExample {
  
    public static class TokenizerMapper extends Mapper<Object, Text, Text, IntWritable> {

        private final static IntWritable one = new IntWritable(1);
        private Text word = new Text();

        public void map(Object key, Text value, Context context) throws IOException, InterruptedException {
            StringTokenizer itr = new StringTokenizer(value.toString());

            while (itr.hasMoreTokens()) {
                word.set(itr.nextToken());
                context.write(word, one);
            }
        }
    }

    public static class IntSumReducer extends Reducer<Text, IntWritable, Text, IntWritable> {
        private IntWritable result = new IntWritable();

        public void reduce(Text key, Iterable<IntWritable> values, Context context) throws IOException, InterruptedException {
            int sum = 0;
            for (IntWritable val : values) {
                sum += val.get();
            }
            result.set(sum);
            context.write(key, result);
        }
    }

    public static void main(String[] args) throws Exception {
        Configuration conf = new Configuration();
        Job job = Job.getInstance(conf, "MapReduce Example");
        job.setJarByClass(MapReduceExample.class);
        job.setMapperClass(TokenizerMapper.class);
        job.setCombinerClass(IntSumReducer.class);
        job.setReducerClass(IntSumReducer.class);
        job.setOutputKeyClass(Text.class);
        job.setOutputValueClass(IntWritable.class);
        FileInputFormat.addInputPath(job, new Path(args[0]));
        FileOutputFormat.setOutputPath(job, new Path(args[1]));
        System.exit(job.waitForCompletion(true) ? 0 : 1);
    }
}

# User Service

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
@RequestMapping("/users")
public class UserService {

    @GetMapping("/{userId}")
    public String getUser(@PathVariable String userId) {
        // Logic to fetch user details from database or any other source
        return "User details for userId: " + userId;
    }

    public static void main(String[] args) {
        SpringApplication.run(UserService.class, args);
    }
}

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
@RequestMapping("/orders")
public class OrderService {

    @GetMapping("/{orderId}")
    public String getOrder(@PathVariable String orderId) {
        // Logic to fetch order details from database or any other source
        return "Order details for orderId: " + orderId;
    }

    public static void main(String[] args) {
        SpringApplication.run(OrderService.class, args);
    }
}

import java.io.BufferedReader;
import java.io.FileReader;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.SQLException;

public class ETLExample {
    public static void main(String[] args) {
        // Extract
        String csvFile = "data.csv";
        String line;
        String csvSplitBy = ",";

        try (BufferedReader br = new BufferedReader(new FileReader(csvFile))) {
            // Transform and Load
            String dbUrl = "jdbc:mysql://localhost:3306/database_name";
            String dbUsername = "username";
            String dbPassword = "password";

            Connection connection = DriverManager.getConnection(dbUrl, dbUsername, dbPassword);

            while ((line = br.readLine()) != null) {
                String[] data = line.split(csvSplitBy);

                // Transform
                String id = data[0];
                String name = data[1].toUpperCase();

                // Load
                PreparedStatement statement = connection.prepareStatement("INSERT INTO Person (id, name) VALUES (?, ?)");
                statement.setString(1, id);
                statement.setString(2, name);
                statement.executeUpdate();
            }

            connection.close();
            System.out.println("ETL process completed successfully.");
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.PrintWriter;

public class DataLakeExample {

    public static void writeToDataLake(String data, String filePath) {
        Configuration configuration = new Configuration();
        try {
            FileSystem fileSystem = FileSystem.get(configuration);
            Path path = new Path(filePath);
            OutputStream outputStream = fileSystem.create(path);
            PrintWriter printWriter = new PrintWriter(outputStream);
            printWriter.write(data);
            printWriter.close();
            fileSystem.close();
            System.out.println("Data written to Data Lake successfully.");
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    public static void readFromDataLake(String filePath) {
        Configuration configuration = new Configuration();
        try {
            FileSystem fileSystem = FileSystem.get(configuration);
            Path path = new Path(filePath);
            BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(fileSystem.open(path)));
            String line;
            while ((line = bufferedReader.readLine()) != null) {
                System.out.println(line);
            }
            bufferedReader.close();
            fileSystem.close();
            System.out.println("Data read from Data Lake successfully.");
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    public static void main(String[] args) {
        String filePath = "/data/example.txt";
        String dataToWrite = "This is an example data to be written to the Data Lake.";

        writeToDataLake(dataToWrite, filePath);
        readFromDataLake(filePath);
    }
}