How to solve deadlock and concurrency problems in Java network programming

Deadlock and concurrency issues are common obstacles in Java network programming and can be solved in the following ways: Deadlock: Use a lock (such as ReentrantLock) or set a timeout to solve it; Concurrency: Use the synchronization keyword or a concurrency library (such as concurrent package) to ensure access security to shared resources.

How to solve deadlock and concurrency problems in Java network programming

In Java network programming, deadlock and concurrency problems are common obstacles. Solving these problems is critical to creating reliable and responsive applications.

Deadlock

Deadlock occurs when two or more threads wait indefinitely for each other. In network programming, this usually happens when two threads are waiting for input from the other.

Solution:

• Use locks: By using locks, you can ensure that only one thread accesses a shared resource at any particular time.
• Timed waiting: If two threads are waiting for each other, you can set a timeout so that one of the threads gives up waiting and continues execution.

Concurrency

Concurrency refers to two or more threads accessing shared resources at the same time. In network programming, this can lead to data races and unpredictable results.

Solution:

• Synchronized code: By using the synchronization keyword (such as synchronized), you can ensure that only one thread executes a block of code at a specific time.
• Use concurrency libraries: Java provides various concurrency libraries, such as the concurrent package, to help manage concurrent operations.

Practical case:

Consider a simple Java server program that uses socket communication. When a client connection is received, the server creates a new thread to handle the connection. If proper concurrency control is not used, multiple threads may compete for the list that the server uses to store client connections.

The following code demonstrates how to use locks to solve this problem:

import java.net.ServerSocket;
import java.net.Socket;
import java.util.Collections;
import java.util.LinkedList;
import java.util.List;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;

public class Server {

    private final int PORT = 1234;
    private final ServerSocket serverSocket;
    private final List<Socket> clients;
    private final Lock lock;

    public Server() throws IOException {
        serverSocket = new ServerSocket(PORT);
        clients = Collections.synchronizedList(new LinkedList<>());
        lock = new ReentrantLock();
    }

    public void start() {
        while (true) {
            try {
                Socket client = serverSocket.accept();
                lock.lock();
                clients.add(client);
                lock.unlock();

                // 为客户端创建一个新线程
                Thread thread = new Thread(() -> handleClient(client));
                thread.start();
            } catch (IOException | InterruptedException e) {
                e.printStackTrace();
            }
        }
    }

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

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