需求说明：
模拟网上商城购物，当用户选好物品提交订单时，每笔订单会自动生成一个唯一的订单编号。而部分电子商务网站在数据高峰期时，一毫秒可能需要处理近千笔的订单
现在简单模拟 5 个订单同时提交，生成唯一订单编号的场景。订单编号的生成规则是以毫秒为单位的当前时间＋订单序号
例如，当前时间的毫秒数是 150000，那第 1 笔订单的编号就是 1500001，第 9 笔订单的编号就是 1500009
实现思路：
项目中创建订单类 Order（订单编号、订单金额、下单用户）
创建订单处理类 ProcessOrder实现Runnable接口，定义Order类型的成员变量和一个Integer静态count作为订单序号（初始1），同时添加产生订单号的方法
产生订单号方法中使用sleep延迟500毫秒，同时添加同步代码块，指定静态变量 count 为同步监视器，同步代码块内则采用系统时间毫秒和订单序号生成订单号操作
在同步代码块外，把订单用户、订单金额和订单编号打印输出
创建测试启动类 TestOrder。在该类的 main() 方法内，使用有参构造方法实例化 5 个 Order 对象。使用ProcessOrder(Order order) 构造方法，实例化 5 个 ProcessOrder 类的对象，并把 5 个 Order 对象依次传给构造方法的参数 order。分别创建5个Thread对象依次传入5个ProcessOrder，启动测试
实现代码：
订单类（Order）
public class Order { //订单编号 private String orderNumber; //订单金额 private double orderAmount; //用户名称 private String username; //无参构造 public Order() { super(); } //有参构造 public Order(String orderNumber, double orderAmount, String username) { super(); this.orderNumber = orderNumber; this.orderAmount = orderAmount; this.username = username; } public String getOrderNumber() { return orderNumber; } public void setOrderNumber(String orderNumber) { this.orderNumber = orderNumber; } public double getOrderAmount() { return orderAmount; } public void setOrderAmount(double orderAmount) { this.orderAmount = orderAmount; } public String getUsername() { return username; } public void setUsername(String username) { this.username = username; } }
订单处理类（ProcessOrder）
public class ProcessOrder implements Runnable{ private Order order; //订单计数器 private static Integer count = 1; public ProcessOrder(Order order) { this.order = order; } @Override public void run() { generateOrderNumber(); } public void generateOrderNumber() { try { //加入线程延迟 Thread.sleep(500); } catch (InterruptedException e) { e.printStackTrace(); } //同步监听器是count变量 synchronized (count) { //生成订单编号 StringBuffer orderNumber = new StringBuffer("").append(System.currentTimeMillis()).append(count++); //将订单编号保存到订单对象中 order.setOrderNumber(orderNumber.toString()); } System.out.printf("%s的订单金额是%.2f元，订单编号是：%s\n",order.getUsername(),order.getOrderAmount(),order.getOrderNumber()); } }
启动运行类（TestOrder）
public class TestOrder { public static void main(String[] args) { //实例化5个订单对象 Order order1 = new Order(null,300,"张三"); Order order2 = new Order(null,400,"李四"); Order order3 = new Order(null,500,"王五"); Order order4 = new Order(null,300,"赵六"); Order order5 = new Order(null,200,"秦七"); //实例化5个Runnable对象 ProcessOrder processOrder1 = new ProcessOrder(order1); ProcessOrder processOrder2 = new ProcessOrder(order2); ProcessOrder processOrder3 = new ProcessOrder(order3); ProcessOrder processOrder4 = new ProcessOrder(order4); ProcessOrder processOrder5 = new ProcessOrder(order5); //实例化5条线程 Thread thread1 = new Thread(processOrder1); Thread thread2 = new Thread(processOrder2); Thread thread3 = new Thread(processOrder3); Thread thread4 = new Thread(processOrder4); Thread thread5 = new Thread(processOrder5); //依次启动线程 thread1.start(); thread2.start(); thread3.start(); thread4.start(); thread5.start(); } }
