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Java 多線程模擬多站點售票系統實戰

編輯：Java 相關知識

專案背景與需求分析

在高併發場景下，多線程對共享資源的訪問必須保證線程安全。本文通過模擬火車票售票系統，展示如何使用 Java 多線程技術實現多站點、多售票窗口的並發售票場景。系統包含三個目的地：北京、上海、天津，每個目的地初始票數 5 張，啟動 5 個售票窗口（線程），每個窗口處理 5 筆交易。

核心類設計

1. 目的地枚舉

package com.zj.tickets;

public enum Destination {
    BEIJING, SHANGHAI, TIANJIN
}

2. 車票實體類

採用不可變模式設計，確保線程安全：

package com.zj.tickets;

public class Ticket {
    private final int original;      // 初始票數
    private int current;             // 當前剩餘票數
    private final Destination destination;

    public Ticket(int nums, Destination dest) {
        this.original = nums;
        this.current = nums;
        this.destination = dest;
    }

    // 售出一張票，返回剩餘票數
    public synchronized int sellOne() {
        return --current;
    }

    public boolean isSoldOut() {
        return current <= 0;
    }

    public int getCurrent() { return current; }
    public int getOriginal() { return original; }
    public Destination getDestination() { return destination; }
}

3. 售票窗口類

實現 Runnable 接口，每個窗口獨立運行：

package com.zj.tickets;

import java.util.*;
import java.util.concurrent.TimeUnit;

public class BookingOffice implements Runnable {
    // 共享票池，所有窗口共用
    private static final Map<Destination, Ticket> ticketPool = new HashMap<>();
    private static final List<BookingOffice> offices = new ArrayList<>();
    
    private final Map<Destination, Integer> salesRecord = new HashMap<>();
    private int ticketsSold = 0;
    private final int officeId;

    static {
        ticketPool.put(Destination.BEIJING, new Ticket(5, Destination.BEIJING));
        ticketPool.put(Destination.SHANGHAI, new Ticket(5, Destination.SHANGHAI));
        ticketPool.put(Destination.TIANJIN, new Ticket(5, Destination.TIANJIN));
    }

    public BookingOffice(int id) {
        this.officeId = id;
        offices.add(this);
    }

    @Override
    public void run() {
        int transactions = 5;
        Random random = new Random();
        
        while (transactions-- > 0) {
            // 模擬客戶隨機選擇目的地
            Destination dest = Destination.values()[random.nextInt(Destination.values().length)];
            log("客戶請求購買 " + dest + " 車票");

            // 模擬查詢延遲
            try { TimeUnit.SECONDS.sleep(1); } 
            catch (InterruptedException e) { Thread.currentThread().interrupt(); }

            // 同步售票邏輯
            Ticket ticket = ticketPool.get(dest);
            synchronized (ticket) {
                if (!ticket.isSoldOut()) {
                    int remaining = ticket.sellOne();
                    ticketsSold++;
                    salesRecord.merge(dest, 1, Integer::sum);
                    log("成功售出 " + dest + " 車票，剩餘：" + remaining);
                } else {
                    log(dest + " 車票已售罄");
                }
            }
        }
        log("窗口關閉 | 總售出：" + ticketsSold + " | 明細：" + salesRecord);
    }

    private void log(String msg) {
        System.out.println("<Office-" + officeId + "> " + msg);
    }
}

4. 主程序啟動類

package com.zj.tickets;

import java.util.concurrent.*;

public class TicketSystem {
    public static void main(String[] args) {
        ExecutorService executor = Executors.newFixedThreadPool(5);
        for (int i = 0; i < 5; i++) {
            executor.submit(new BookingOffice(i));
        }
        executor.shutdown();
    }
}