报告三还没写完，先存个档

2 years ago · 551ac9b1bd
commit 551ac9b1bd
24 changed files with 800 additions and 0 deletions
--- a/.gitignore
+++ b/.gitignore
@ -0,0 +1,33 @@
+HELP.md
+target/
+!.mvn/wrapper/maven-wrapper.jar
+!**/src/main/**/target/
+!**/src/test/**/target/
+
+### STS ###
+.apt_generated
+.classpath
+.factorypath
+.project
+.settings
+.springBeans
+.sts4-cache
+
+### IntelliJ IDEA ###
+.idea
+*.iws
+*.iml
+*.ipr
+
+### NetBeans ###
+/nbproject/private/
+/nbbuild/
+/dist/
+/nbdist/
+/.nb-gradle/
+build/
+!**/src/main/**/build/
+!**/src/test/**/build/
+
+### VS Code ###
+.vscode/
--- a/exp1-oop/pom.xml
+++ b/exp1-oop/pom.xml
@ -0,0 +1,20 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+    <parent>
+        <groupId>net.lensfrex</groupId>
+        <artifactId>lesson</artifactId>
+        <version>1.0-SNAPSHOT</version>
+    </parent>
+
+    <artifactId>exp1-oop</artifactId>
+
+    <properties>
+        <maven.compiler.source>8</maven.compiler.source>
+        <maven.compiler.target>8</maven.compiler.target>
+        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+    </properties>
+
+</project>
--- a/exp1-oop/src/main/java/net/lensfrex/AbstractExtends.java
+++ b/exp1-oop/src/main/java/net/lensfrex/AbstractExtends.java
@ -0,0 +1,30 @@
+package net.lensfrex;
+
+public class AbstractExtends {
+    protected void run() {
+        Father father = new Child();
+
+        father.method1();
+        father.method2();
+    }
+}
+
+// ------------------------------------------
+abstract class Father {
+    public abstract void method1();
+
+    public abstract void method2();
+}
+
+// -------------------------------------------
+class Child extends Father {
+    @Override
+    public void method1() {
+        System.out.println("Do some thing in method1");
+    }
+
+    @Override
+    public void method2() {
+        System.out.println("Do some thing in method2");
+    }
+}
--- a/exp1-oop/src/main/java/net/lensfrex/Interface.java
+++ b/exp1-oop/src/main/java/net/lensfrex/Interface.java
@ -0,0 +1,26 @@
+package net.lensfrex;
+
+public class Interface {
+    protected void run() {
+        AnInterface anInterface = new AnInterface() {
+            @Override
+            public void method1() {
+                System.out.println("Do some thing in method1");
+            }
+
+            @Override
+            public void method2() {
+                System.out.println("Do some thing in method2");
+            }
+        };
+
+        anInterface.method1();
+        anInterface.method2();
+    }
+}
+
+interface AnInterface {
+    void method1();
+
+    void method2();
+}
--- a/exp1-oop/src/main/java/net/lensfrex/Main.java
+++ b/exp1-oop/src/main/java/net/lensfrex/Main.java
@ -0,0 +1,51 @@
+package net.lensfrex;
+
+import java.io.BufferedReader;
+import java.io.InputStreamReader;
+
+public class Main {
+    public static void main(String[] args) throws Exception {
+        if (args.length > 0) {
+            execute(args[0]);
+        } else {
+            System.out.println("Witch to run? (1, 2, 3)");
+            BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
+
+            execute(reader.readLine());
+        }
+    }
+
+    private static void execute(String option) {
+        Main main = new Main();
+
+        switch (option) {
+            case "1":
+                main.run1();
+                break;
+            case "2":
+                main.run2();
+                break;
+            case "3":
+                main.run3();
+                break;
+            default:
+                System.out.printf("Invalid input for '%s'%n", option);
+        }
+    }
+
+    private void run1() {
+        Rectangle rectangle = new Rectangle(3, 4);
+
+        System.out.println("rectangleHeight: " + rectangle.getHeight());
+        System.out.println("rectangleWidth: " + rectangle.getWidth());
+        System.out.println("rectangleSize: " + rectangle.getSize());
+    }
+
+    private void run2() {
+        new Interface().run();
+    }
+
+    private void run3() {
+        new AbstractExtends().run();
+    }
+}
--- a/exp1-oop/src/main/java/net/lensfrex/Rectangle.java
+++ b/exp1-oop/src/main/java/net/lensfrex/Rectangle.java
@ -0,0 +1,33 @@
+package net.lensfrex;
+
+public class Rectangle {
+    private float height = 0;
+    private float width = 0;
+
+    public Rectangle() {}
+
+    public Rectangle(float height, float width) {
+        this.height = height;
+        this.width = width;
+    }
+
+    public float getSize() {
+        return height * width;
+    }
+
+    public float getHeight() {
+        return height;
+    }
+
+    public void setHeight(float height) {
+        this.height = height;
+    }
+
+    public float getWidth() {
+        return width;
+    }
+
+    public void setWidth(float width) {
+        this.width = width;
+    }
+}
--- a/exp2-thread/pom.xml
+++ b/exp2-thread/pom.xml
@ -0,0 +1,20 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+    <parent>
+        <groupId>net.lensfrex</groupId>
+        <artifactId>lesson</artifactId>
+        <version>1.0-SNAPSHOT</version>
+    </parent>
+
+    <artifactId>exp2-thread</artifactId>
+
+    <properties>
+        <maven.compiler.source>8</maven.compiler.source>
+        <maven.compiler.target>8</maven.compiler.target>
+        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+    </properties>
+
+</project>
--- a/exp2-thread/src/main/java/net/lensfrex/Main.java
+++ b/exp2-thread/src/main/java/net/lensfrex/Main.java
@ -0,0 +1,42 @@
+package net.lensfrex;
+
+import java.io.BufferedReader;
+import java.io.InputStreamReader;
+
+public class Main {
+    public static void main(String[] args) throws Exception {
+        System.out.println("Thread Lesson report");
+
+        if (args.length > 0) {
+            execute(args[0]);
+        } else {
+            System.out.println("Witch to run? (1, 2)");
+            BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
+
+            execute(reader.readLine());
+        }
+    }
+
+    private static void execute(String option) {
+        Main main = new Main();
+
+        switch (option) {
+            case "1":
+                main.run1();
+                break;
+            case "2":
+                main.run2();
+                break;
+            default:
+                System.out.printf("Invalid input for '%s'%n", option);
+        }
+    }
+
+    private void run1() {
+        new RabbitAndTortoise().runTest();
+    }
+
+    private void run2() {
+        new Ticket().runTest();
+    }
+}
--- a/exp2-thread/src/main/java/net/lensfrex/RabbitAndTortoise.java
+++ b/exp2-thread/src/main/java/net/lensfrex/RabbitAndTortoise.java
@ -0,0 +1,42 @@
+package net.lensfrex;
+
+public class RabbitAndTortoise {
+    public void runTest() {
+        Animal rabbit = new Animal("Rabbit", 16, 32);
+        Animal tortoise = new Animal("Tortoise", 8, 32);
+
+        new Thread(rabbit).start();
+        new Thread(tortoise).start();
+    }
+}
+
+class Animal implements Runnable {
+    private final String name;
+
+    private final int speed;
+    private final int targetDistance;
+
+    private int totalDistance = 0;
+
+    public Animal(String name, int speed, int targetDistance) {
+        this.name = name;
+        this.speed = speed;
+        this.targetDistance = targetDistance;
+    }
+
+    @Override
+    public void run() {
+        while (totalDistance <= targetDistance) {
+            try {
+                Thread.sleep((int) (Math.random() * 1000) + 500);
+            } catch (Exception ignored) {
+                return;
+            }
+
+            totalDistance += speed;
+            System.out.printf("[%s] has run %d%n", name, totalDistance);
+        }
+
+        System.out.printf("[%s] has finish the game.%n", name);
+    }
+}
--- a/exp2-thread/src/main/java/net/lensfrex/Ticket.java
+++ b/exp2-thread/src/main/java/net/lensfrex/Ticket.java
@ -0,0 +1,40 @@
+package net.lensfrex;
+
+public class Ticket {
+    public void runTest() {
+        TicketOffice ticketOffice = new TicketOffice();
+        new Thread(ticketOffice, "0").start();
+        new Thread(ticketOffice, "1").start();
+        new Thread(ticketOffice, "2").start();
+    }
+}
+
+class TicketOffice implements Runnable {
+    private static int ticket = 8;
+
+    @Override
+    public void run() {
+        String name = Thread.currentThread().getName();
+        while(sellTicket(name));
+    }
+
+    private boolean sellTicket(String name) {
+        synchronized (this) {
+            if (ticket <= 0) {
+                System.out.printf("[%s]: Ticket was sold out.%n", name);
+                return false;
+            }
+
+            System.out.printf("TicketOffice '%s' is selling ticket No.%s%n", name, ticket);
+            ticket--;
+
+            try {
+                Thread.sleep(128);
+            } catch (Exception ignored) {
+                return false;
+            }
+        }
+
+        return true;
+    }
+}
--- a/exp3-network/pom.xml
+++ b/exp3-network/pom.xml
@ -0,0 +1,32 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+    <parent>
+        <groupId>net.lensfrex</groupId>
+        <artifactId>lesson</artifactId>
+        <version>1.0-SNAPSHOT</version>
+    </parent>
+
+    <artifactId>exp3-network</artifactId>
+
+    <properties>
+        <maven.compiler.source>8</maven.compiler.source>
+        <maven.compiler.target>8</maven.compiler.target>
+        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+    </properties>
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-compiler-plugin</artifactId>
+                <configuration>
+                    <source>9</source>
+                    <target>9</target>
+                </configuration>
+            </plugin>
+        </plugins>
+    </build>
+
+</project>
--- a/exp3-network/src/main/java/net/lensfrex/Main.java
+++ b/exp3-network/src/main/java/net/lensfrex/Main.java
@ -0,0 +1,54 @@
+package net.lensfrex;
+
+import javafx.application.Application;
+import net.lensfrex.socket.Client;
+import net.lensfrex.socket.Server;
+import net.lensfrex.socket.Util;
+
+import java.io.BufferedReader;
+import java.io.InputStreamReader;
+
+public class Main {
+    public static void main(String[] args) throws Exception {
+        System.out.println("Thread Lesson report");
+
+        if (args.length > 0) {
+            execute(args[0]);
+        } else {
+            System.out.println("Witch to run? (1server, 1client, 2)");
+            BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
+
+            execute(reader.readLine());
+        }
+    }
+
+    private static void execute(String option) {
+        Main main = new Main();
+
+        switch (option) {
+            case "1server":
+                main.run1Server();
+                break;
+            case "1client":
+                main.run1Client();
+                break;
+            case "2":
+                main.run2();
+                break;
+            default:
+                System.out.printf("Invalid input for '%s'%n", option);
+        }
+    }
+
+    private void run1Server() {
+        new Server().start();
+    }
+
+    private void run1Client() {
+        new Client().start();
+    }
+
+    private void run2() {
+        System.out.println(Util.randomString(128));
+    }
+}
--- a/exp3-network/src/main/java/net/lensfrex/socket/Client.java
+++ b/exp3-network/src/main/java/net/lensfrex/socket/Client.java
@ -0,0 +1,15 @@
+package net.lensfrex.socket;
+
+import javafx.application.Application;
+import javafx.stage.Stage;
+
+public class Client extends Application {
+    public void start() {
+        launch();
+    }
+
+    @Override
+    public void start(Stage primaryStage) throws Exception {
+
+    }
+}
--- a/exp3-network/src/main/java/net/lensfrex/socket/Constant.java
+++ b/exp3-network/src/main/java/net/lensfrex/socket/Constant.java
@ -0,0 +1,15 @@
+package net.lensfrex.socket;
+
+import java.nio.charset.StandardCharsets;
+
+public class Constant {
+    public static final byte[] MAGIC_HEADER = "AETH".getBytes(StandardCharsets.UTF_8);
+
+    public static final int OPCODE_LENGTH = 4;
+    public static final byte[] OPCODE_REQUEST_MESSAGE = "RMSG".getBytes(StandardCharsets.UTF_8);
+    public static final byte[] OPCODE_SEND_MESSAGE = "SMSG".getBytes(StandardCharsets.UTF_8);
+    public static final byte[] OPCODE_ONLINE = "ONLI".getBytes(StandardCharsets.UTF_8);
+    public static final byte[] OPCODE_OFFLINE = "OFFL".getBytes(StandardCharsets.UTF_8);
+
+    public static final byte[] MESSAGE_OK = "OK".getBytes(StandardCharsets.UTF_8);
+}
--- a/exp3-network/src/main/java/net/lensfrex/socket/Data.java
+++ b/exp3-network/src/main/java/net/lensfrex/socket/Data.java
@ -0,0 +1,7 @@
+package net.lensfrex.socket;
+
+import java.io.Serializable;
+
+public class Data implements Serializable {
+//    private final byte[] data
+}
--- a/exp3-network/src/main/java/net/lensfrex/socket/DataPack.java
+++ b/exp3-network/src/main/java/net/lensfrex/socket/DataPack.java
@ -0,0 +1,27 @@
+package net.lensfrex.socket;
+
+import java.io.Serializable;
+
+public class DataPack implements Serializable {
+    private final byte[] opcode;
+    private final int dataLength;
+    private final byte[] data;
+
+    public DataPack(byte[] opcode, byte[] data) {
+        this.opcode = opcode;
+        this.dataLength = data.length;
+        this.data = data;
+    }
+
+    public byte[] getOpcode() {
+        return opcode;
+    }
+
+    public int getDataLength() {
+        return dataLength;
+    }
+
+    public byte[] getData() {
+        return data;
+    }
+}
--- a/exp3-network/src/main/java/net/lensfrex/socket/MessageData.java
+++ b/exp3-network/src/main/java/net/lensfrex/socket/MessageData.java
@ -0,0 +1,32 @@
+package net.lensfrex.socket;
+
+public class MessageData {
+    private final int idLength;
+    private final byte[] idData;
+
+    private final int messageLength;
+    private final byte[] messageData;
+
+    public MessageData(int idLength, byte[] idData, int messageLength, byte[] messageData) {
+        this.idLength = idLength;
+        this.idData = idData;
+        this.messageLength = messageLength;
+        this.messageData = messageData;
+    }
+
+    public int getIdLength() {
+        return idLength;
+    }
+
+    public byte[] getIdData() {
+        return idData;
+    }
+
+    public int getMessageLength() {
+        return messageLength;
+    }
+
+    public byte[] getMessageData() {
+        return messageData;
+    }
+}
--- a/exp3-network/src/main/java/net/lensfrex/socket/Request.java
+++ b/exp3-network/src/main/java/net/lensfrex/socket/Request.java
@ -0,0 +1,5 @@
+package net.lensfrex.socket;
+
+public class Request {
+
+}
--- a/exp3-network/src/main/java/net/lensfrex/socket/RequestBody.java
+++ b/exp3-network/src/main/java/net/lensfrex/socket/RequestBody.java
@ -0,0 +1,6 @@
+package net.lensfrex.socket;
+
+import java.io.Serializable;
+
+public class RequestBody implements Serializable {
+}
--- a/exp3-network/src/main/java/net/lensfrex/socket/Server.java
+++ b/exp3-network/src/main/java/net/lensfrex/socket/Server.java
@ -0,0 +1,158 @@
+package net.lensfrex.socket;
+
+import java.io.*;
+import java.net.ServerSocket;
+import java.net.Socket;
+import java.nio.charset.StandardCharsets;
+import java.util.Arrays;
+import java.util.HashSet;
+
+public class Server {
+    private static boolean stop = false;
+
+    public void start() {
+        Server.stop = false;
+
+        try (ServerSocket serverSocket = new ServerSocket(2333)) {
+            while (!stop) {
+                // Start a new thread to service more than one client
+                new ServerThread(serverSocket.accept()).start();
+            }
+        } catch (Exception e) {
+            System.err.println("Some exception happened: " + e);
+        }
+    }
+
+    public void stop() {
+        Server.stop = true;
+    }
+}
+
+class ServerThread extends Thread {
+    private static final HashSet<User> onlineUsers = new HashSet();
+
+    private final Socket socket;
+
+    public ServerThread(Socket socket) {
+        this.socket = socket;
+    }
+
+    @Override
+    public void run() {
+        try (InputStream inputStream = socket.getInputStream(); OutputStream outputStream = socket.getOutputStream()) {
+            byte[] clientMagicHeader = new byte[Constant.MAGIC_HEADER.length];
+            if (inputStream.read(clientMagicHeader) == -1) {
+                return;
+            }
+
+            if (!Arrays.equals(clientMagicHeader, Constant.MAGIC_HEADER)) {
+                return;
+            }
+
+            byte[] clientOpcode = new byte[Constant.OPCODE_LENGTH];
+            if (inputStream.read(clientOpcode) == -1) {
+                return;
+            }
+
+            int dataLength = getLengthField(inputStream);
+            if (dataLength == -1) {
+                return;
+            }
+
+            this.executeAction(clientOpcode, dataLength, inputStream, outputStream);
+        } catch (IOException e) {
+            throw new RuntimeException(e);
+        }
+    }
+
+    private void executeAction(byte[] opcode, int dataLength, InputStream inputStream, OutputStream outputStream) throws IOException {
+        byte[] data = this.readRequest(dataLength, inputStream);
+
+        if (Arrays.equals(Constant.OPCODE_ONLINE, opcode)) {
+            this.login(new String(data));
+            this.sendResponse(Constant.MESSAGE_OK, outputStream);
+        } else if (Arrays.equals(Constant.OPCODE_OFFLINE, opcode)) {
+            this.logout(new String(data));
+        } else if (Arrays.equals(Constant.OPCODE_REQUEST_MESSAGE, opcode)) {
+
+        }
+    }
+
+    private void login(String id) {
+        User user = new User(id);
+        onlineUsers.add(user);
+
+        System.out.printf("User '%s' login.%n", user.getId());
+    }
+
+    private void logout(String id) {
+        User user = new User(id);
+        onlineUsers.add(user);
+        System.out.printf("User '%s' logout.%n", user.getId());
+    }
+
+    private void
+
+    private int sendMessage(User user, OutputStream outputStream) throws IOException {
+        if (!onlineUsers.contains(user)) {
+
+        }
+
+        int responseLength = this.sendResponse(Util.randomString(128), outputStream);
+
+        return responseLength;
+    }
+
+    private int getLengthField(InputStream inputStream) throws IOException {
+        byte[] tmp = new byte[4];
+        if (inputStream.read(tmp) == -1) {
+            return -1;
+        }
+
+        return Util.bytesToInt32(tmp);
+    }
+
+    private void receiveMessage(DataPack dataPack) {
+        byte[] data = dataPack.getData();
+
+        User user = new User();
+
+        String message = new String(data);
+        System.out.printf("Receive message '%s' from: '%s'%n", user.getId(), message);
+        System.out.println("----------------");
+    }
+
+    private DataPack readRequest(InputStream inputStream) throws IOException {
+        byte[] clientOpcode = new byte[Constant.OPCODE_LENGTH];
+        if (inputStream.read(clientOpcode) == -1) {
+            return null;
+        }
+
+        int dataLength = this.getLengthField(inputStream);
+
+        byte[] data = new byte[dataLength];
+        inputStream.read(data);
+
+        return new DataPack(clientOpcode, data);
+    }
+
+    private int sendResponse(String message, OutputStream outputStream) throws IOException {
+        return this.sendResponse(message.getBytes(StandardCharsets.UTF_8), outputStream);
+    }
+
+    private int sendResponse(byte[] data, OutputStream outputStream) throws IOException {
+        DataPack dataPack = new DataPack(Constant.OPCODE_SEND_MESSAGE, data);
+
+        return this.sendResponse(dataPack, outputStream);
+    }
+
+    private int sendResponse(DataPack dataPack, OutputStream outputStream) throws IOException {
+        outputStream.write(Constant.MAGIC_HEADER);
+        outputStream.write(dataPack.getOpcode());
+
+        outputStream.write(Util.int32ToBytes(dataPack.getDataLength()));
+        outputStream.write(dataPack.getData());
+
+        return dataPack.getDataLength();
+    }
+}
--- a/exp3-network/src/main/java/net/lensfrex/socket/User.java
+++ b/exp3-network/src/main/java/net/lensfrex/socket/User.java
@ -0,0 +1,13 @@
+package net.lensfrex.socket;
+
+public class User {
+    private final String id;
+
+    public User(String id) {
+        this.id = id;
+    }
+
+    public String getId() {
+        return id;
+    }
+}
--- a/exp3-network/src/main/java/net/lensfrex/socket/Util.java
+++ b/exp3-network/src/main/java/net/lensfrex/socket/Util.java
@ -0,0 +1,69 @@
+package net.lensfrex.socket;
+
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.io.InputStream;
+import java.util.Random;
+
+public class Util {
+    private static final char[] alphabet = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789".toCharArray();
+    private static final Random random = new Random();
+
+    public static String randomString(int length) {
+        StringBuilder sb = new StringBuilder();
+        for (int i = 0; i < length; i++) {
+            sb.append(alphabet[random.nextInt(alphabet.length)]);
+        }
+
+        return sb.toString();
+    }
+
+    public static int bytesToInt32(byte[] bytes) {
+        int result = 0;
+        for (int i = 0; i < 4; i++) {
+            int shift = (3 - i) * 8;
+            result += (bytes[i] & 0xFF) << shift;
+        }
+
+        return result;
+    }
+
+    public static byte[] int32ToBytes(int i) {
+        byte[] result = new byte[4];
+        result[0] = (byte) ((i >> 24) & 0xFF);
+        result[1] = (byte) ((i >> 16) & 0xFF);
+        result[2] = (byte) ((i >> 8) & 0xFF);
+        result[3] = (byte) (i & 0xFF);
+
+        return result;
+    }
+
+    public static byte[] readAllData(InputStream inputStream) {
+        return readAllData(inputStream, 5);// read every 5kb in default
+    }
+
+    public static byte[] readAllData(InputStream inputStream, int byteAllocation) {
+//        On Java 9 and newer version, can be more simply:
+//        try (ByteArrayOutputStream byteArrayInputStream = new ByteArrayOutputStream(); inputStream) {
+
+        try (ByteArrayOutputStream byteArrayInputStream = new ByteArrayOutputStream()) {
+            byte[] bytes = new byte[1024 * byteAllocation];
+
+            for (int length; (length = inputStream.read(bytes)) != -1; ) {
+                byteArrayInputStream.write(bytes, 0, length);
+            }
+
+            byteArrayInputStream.flush();
+
+            return byteArrayInputStream.toByteArray();
+        } catch (Exception e) {
+            e.printStackTrace();
+            return null;
+        } finally {
+            try {
+                inputStream.close();
+            } catch (IOException ignored) {
+            }
+        }
+    }
+}
--- a/pom.xml
+++ b/pom.xml
@ -0,0 +1,23 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+
+    <groupId>net.lensfrex</groupId>
+    <artifactId>lesson</artifactId>
+    <version>1.0-SNAPSHOT</version>
+    <packaging>pom</packaging>
+    <modules>
+        <module>exp1-oop</module>
+        <module>exp2-thread</module>
+        <module>exp3-network</module>
+    </modules>
+
+    <properties>
+        <maven.compiler.source>8</maven.compiler.source>
+        <maven.compiler.target>8</maven.compiler.target>
+        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+    </properties>
+
+</project>
--- a/src/main/java/net/lensfrex/Main.java
+++ b/src/main/java/net/lensfrex/Main.java
@ -0,0 +1,7 @@
+package net.lensfrex;
+
+public class Main {
+    public static void main(String[] args) {
+        System.out.println("Hello world!");
+    }
+}