Question

我对Java不太满意，我想编写一个简单的客户端-服务器程序（迄今为止的书），但是我不知道如何在线程之间共享变量termins（或我在哪里编写）错误）。任何建议都会被接受。我已经坚持了几个小时。

这是我的代码：

Termin.java：

public class Termin {
public volatile int hour;
public volatile boolean reserved = false;
public volatile String user = null;

public Termin(int hour) {
    this.hour = hour;
}

public void setHour(int value) {
    this.hour = value;
}
...

Server.java：

public class Server {
public static final int PORT = 4444;
public volatile static Termin[] termins = new Termin[] {
        new Termin(8),
        new Termin(9),
        new Termin(10),
        new Termin(11),
        new Termin(12),
        new Termin(13),
        new Termin(14),
        new Termin(15),
        new Termin(16),
        new Termin(17),
};

public static void main(String[] args) throws IOException{
    Server server = new Server();
    server.runServer();
}

public void runServer() throws IOException{
    ServerSocket serverSocket = new ServerSocket(PORT);
    System.out.println("Server up and ready for connections...");
    while(true){
        Socket socket = serverSocket.accept();
        new ServerThread(socket).start();
    }
}
}

ServerThread.java：

public class ServerThread extends Thread {
Socket socket;
ServerThread(Socket socket){
    this.socket = socket;
}
public void run(){
    try {
        String message = null;
        PrintWriter printWriter = new PrintWriter(socket.getOutputStream(), true);
        BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(socket.getInputStream()));
        System.out.println("user '" + bufferedReader.readLine() + "' is now connected to the server");
        while ((message = bufferedReader.readLine()) != null) {
            System.out.println("incoming client message: " + message);
            printWriter.println(message);
        }
        socket.close();
    } catch (IOException e) {
        e.printStackTrace();
    }
}

我如何连接 Clint.java：

public class Client {
public static void main(String[] args) throws UnknownHostException, IOException{
    String name = args[0];
    Socket socket = new Socket("localhost", Server.PORT);
    BufferedReader bufferedReaderFromClient = new BufferedReader(new InputStreamReader(socket.getInputStream()));
    PrintWriter printWriter = new PrintWriter(socket.getOutputStream(), true);
    printWriter.println(name);
    BufferedReader bufferedReaderFromCmdPrompt = new java.io.BufferedReader(new InputStreamReader(System.in));

还有 Client.java 中的片段，我在其中更改了termins的值：

try {
                        String newReaderInput = bufferedReaderFromCmdPrompt.readLine();
                        printWriter.println(newReaderInput);
                        int var = Integer.parseInt(bufferedReaderFromClient.readLine());
                        if(var == 10 || var == 1 || var == 2 || var == 3 || var == 4 || var == 5 || var == 6 || var == 7 || var == 8 || var == 9 ) {   
                            if(Server.termins[var].reserved == false) {
                                Server.termins[var-1].setReserved(true);
                                Server.termins[var-1].setUser(name);
                                System.out.println("\n\nTermin reserved.\n\n");
                                x=0;
                            } else {
                                System.out.println("\n\nError. Termin already booked\n\n");
                            }
                        } else {
                            System.out.println("\n\nError. No termin like this.!!!\n\n");
                            displayYourTermins(name);
                        }
                    } catch (NumberFormatException e) {
                        System.out.println("\n\nError. Write a number!!!\n\n");
                        displayYourTermins(name);
                    }

Answer 1

您可以通过您的自定义线程类的构造函数在不同线程之间共享变量。

例如，您的 Server.java 要使用 ServerThread.java 发送对象，您应该将此对象作为构造函数的参数传递。

import java.io.IOException;
import java.net.ServerSocket;
import java.net.Socket;

public class Server {

    private static final int PORT = 4444;

    public static void main(String[] args) throws IOException {
        ServerSocket serverSocket = new ServerSocket(PORT);
        try {
            while(true) {
                Socket socket = serverSocket.accept();

                // Your Object that you want to share with another thread
                Termin termin = new Termin(20);

                // Pass objects in constructor of another thread, So that another thread can use it.
                // If you want to share more than one object, then change constructor and pass it via constructor.
                new ServerThread(socket, termin).start();
            }
        } catch(Exception e) {
            System.out.println("Exception occurred in Server Program");
            e.printStackTrace();
        } finally {
            serverSocket.close();
            System.out.println("Server Program Ended");
        }
    }
}

如果要从 ServerThread.java 使用此对象，则应保存该对象的引用，然后可以在另一个线程中使用此对象。例如： ServerThread.java

public class ServerThread extends Thread {
    private Socket socket;
    private Termin termin;

    public ServerThread(Socket socket, Termin termin) {
        this.socket = socket;
        this.termin = termin;
    }

    @Override
    public void run() {
        // Your logic...
        // Here you can use termin which was passed from main thread.
        // If you change termin object here, it will also affect termin object in main thread.
    }
}

在这里您可以使用在主线程和ServerThread线程之间共享的termin和socket。

如何在线程JAVA之间共享变量beet？

1 个答案: