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Java知识体系结构梳理如下：
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基础语法：Java的基本语法，包括数据类型、运算符、控制语句、数组等。
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面向对象编程：Java是一种面向对象的编程语言，需要掌握类、对象、继承、多态等概念。
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异常处理：Java提供了异常处理机制，需要掌握异常的分类、处理方式等。
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集合框架：Java提供了丰富的集合框架，包括List、Set、Map等，需要了解其特点和使用方法。
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IO流：Java提供了文件读写和网络通信等IO流，需要掌握其使用方法。
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多线程：Java提供了多线程编程机制，需要掌握线程的创建、同步、互斥等概念。
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数据库编程：Java可以通过JDBC连接数据库，需要掌握SQL语句的编写和Java操作数据库的方法。
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GUI编程：Java提供了Swing和AWT两种GUI库，需要掌握GUI组件的使用方法和事件处理机制。
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网络编程：Java提供了Socket和RMI两种网络编程方式，需要了解其使用方法和原理。
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Web开发：Java可以用于Web开发，需要掌握Servlet、JSP、Spring、Struts等Web开发框架。
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安全编程：Java提供了安全编程的机制，包括加密、数字签名等，需要了解其使用方法和原理。
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性能调优：Java程序的性能调优是一个重要的话题，需要掌握优化技巧和工具的使用方法。
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设计模式：Java程序设计中常用的设计模式，包括单例模式、工厂模式、观察者模式等，需要了解其使用方法和原理。
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其他：Java还包括XML解析、Web服务、分布式计算等方面的知识，需要根据实际需求进行学习和掌握。
Java网络编程聊天室可以通过以下步骤实现发送文件功能：
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在聊天室客户端界面添加一个文件选择按钮，允许用户选择要发送的文件。
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当用户选择要发送的文件后，客户端将文件转换为字节数组，并向服务器发送一个包含文件名和字节数组的消息。
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服务器接收到消息后，将文件保存到指定的目录下，并向所有在线客户端广播一个包含文件名和文件路径的消息。
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在客户端界面上，接收到服务器广播的文件消息后，显示文件名和下载链接，用户可以点击链接下载文件。
下面是一个简单的Java代码示例：
聊天室客户端：
import java.awt.BorderLayout;
import java.awt.EventQueue;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.Socket;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.Base64;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;import javax.swing.JButton;
import javax.swing.JFileChooser;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;public class ChatClient extends JFrame {private static final long serialVersionUID = 1L;private JTextArea chatArea;private JButton fileButton;private JFileChooser fileChooser;private ExecutorService executor;private Socket socket;private OutputStream outputStream;private InputStream inputStream;private String userName;public ChatClient(String userName) {this.userName = userName;initComponents();}private void initComponents() {setTitle("Chat Client");setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);setSize(400, 400);chatArea = new JTextArea();JScrollPane scrollPane = new JScrollPane(chatArea);add(scrollPane, BorderLayout.CENTER);JPanel panel = new JPanel();fileButton = new JButton("Send File");fileChooser = new JFileChooser();fileButton.addActionListener(new ActionListener() {public void actionPerformed(ActionEvent e) {int returnVal = fileChooser.showOpenDialog(ChatClient.this);if (returnVal == JFileChooser.APPROVE_OPTION) {File file = fileChooser.getSelectedFile();try {sendFile(file);} catch (IOException ex) {ex.printStackTrace();}}}});panel.add(fileButton);add(panel, BorderLayout.SOUTH);setVisible(true);executor = Executors.newFixedThreadPool(2);executor.execute(new ReceiveMessageTask());executor.execute(new SendMessageTask());}private void sendFile(File file) throws IOException {byte[] fileBytes = Files.readAllBytes(file.toPath());String fileName = file.getName();String fileData = Base64.getEncoder().encodeToString(fileBytes);String message = "FILE " + fileName + " " + fileData;outputStream.write(message.getBytes());outputStream.flush();}private void receiveFile(String fileName, String fileData) throws IOException {Path filePath = Paths.get("received", fileName);byte[] fileBytes = Base64.getDecoder().decode(fileData);Files.write(filePath, fileBytes);String message = "FILE " + fileName + " " + filePath.toAbsolutePath();broadcastMessage(message);}private void broadcastMessage(String message) throws IOException {outputStream.write(message.getBytes());outputStream.flush();}private class ReceiveMessageTask implements Runnable {public void run() {try {socket = new Socket("localhost", 8000);outputStream = socket.getOutputStream();inputStream = socket.getInputStream();String message = "JOIN " + userName;outputStream.write(message.getBytes());outputStream.flush();while (true) {byte[] buffer = new byte[1024];int len = inputStream.read(buffer);if (len > 0) {String msg = new String(buffer, 0, len);if (msg.startsWith("FILE ")) {String[] parts = msg.split(" ");String fileName = parts[1];String fileData = parts[2];receiveFile(fileName, fileData);} else {chatArea.append(msg + "\n");}}}} catch (IOException e) {e.printStackTrace();} finally {try {socket.close();} catch (IOException e) {e.printStackTrace();}}}}private class SendMessageTask implements Runnable {public void run() {try {while (true) {String message = System.console().readLine();if (message != null && !message.isEmpty()) {if (message.startsWith("/")) {if (message.startsWith("/quit")) {outputStream.write("QUIT".getBytes());outputStream.flush();executor.shutdownNow();break;}} else {message = "CHAT " + message;outputStream.write(message.getBytes());outputStream.flush();}}}} catch (IOException e) {e.printStackTrace();}}}public static void main(String[] args) {EventQueue.invokeLater(new Runnable() {public void run() {new ChatClient("User1");}});}}
聊天室服务器：
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.ArrayList;
import java.util.List;public class ChatServer {private List<ClientHandler> clients = new ArrayList<>();public void start() {try {ServerSocket serverSocket = new ServerSocket(8000);System.out.println("Server started on port 8000.");while (true) {Socket socket = serverSocket.accept();ClientHandler client = new ClientHandler(socket);clients.add(client);System.out.println("New client joined: " + client.getName());broadcastMessage(client.getName() + " joined the chat.");client.start();}} catch (IOException e) {e.printStackTrace();}}private void broadcastMessage(String message) {for (ClientHandler client : clients) {client.sendMessage(message);}}private class ClientHandler extends Thread {private Socket socket;private String name;private InputStream inputStream;private OutputStream outputStream;public ClientHandler(Socket socket) {this.socket = socket;}public String getName() {return name;}public void run() {try {inputStream = socket.getInputStream();outputStream = socket.getOutputStream();byte[] buffer = new byte[1024];int len = inputStream.read(buffer);if (len > 0) {String message = new String(buffer, 0, len);if (message.startsWith("JOIN ")) {name = message.substring(5).trim();sendMessage("Welcome to the chat, " + name + "!");broadcastMessage(name + " joined the chat.");}}while (true) {len = inputStream.read(buffer);if (len > 0) {String message = new String(buffer, 0, len);if (message.startsWith("CHAT ")) {message = name + ": " + message.substring(5);broadcastMessage(message);} else if (message.startsWith("FILE ")) {String[] parts = message.split(" ");String fileName = parts[1];String fileData = parts[2];broadcastMessage("FILE " + fileName + " " + socket.getInetAddress().getHostAddress());} else if (message.startsWith("QUIT")) {broadcastMessage(name + " left the chat.");break;}}}} catch (IOException e) {e.printStackTrace();} finally {try {socket.close();clients.remove(this);} catch (IOException e) {e.printStackTrace();}}}public void sendMessage(String message) throws IOException {outputStream.write(message.getBytes());outputStream.flush();}}public static void main(String[] args) {new ChatServer().start();}}