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();

}

}