学习例子是参照《thinking in java》中修改的，先贴上运行结果：
注意看红框之中的内容，这个仿真要达到这样一个目的：
1.客户队列（无优先级）：每隔300MILLS生产一个客户
2.正在服务的出纳员队列（有优先级）：队列头始终是服务人数最多的那个出纳员，因为在队列调整的时候需要将服务人数最多的出纳员调整出去做其他的事情（相当于找个轻松的事情做，放松下）
3.做其他事情的出纳员列表（有优先级）：队列头始终是服务人数最少的那个出纳员，因为在队列调整的时候需要讲服务人数最少的出纳员调整去服务（为客户办理业务）
队列调整时间为每1秒调整一次
下面贴上代码：
package com.xt.thinks21_8; import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.Comparator;
import java.util.LinkedList;
import java.util.PriorityQueue;
import java.util.Queue;
import java.util.Random;
import java.util.concurrent.ArrayBlockingQueue;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit; /**
* 消费者（客户）
*
* @author Administrator
*
*/
class Customer {
private final int serviceTime;// 服务时间（客户的业务办理时间） public Customer(int tm) {
serviceTime = tm;
} public int getServiceTime() {
return serviceTime;
} public String toString() {
return " ● ";
}
} /**
* 消费者队列（客户排成一条队伍）
*
* @author Administrator
*
*/
class CustomerLine extends ArrayBlockingQueue<Customer> {
/**
*
*/
private static final long serialVersionUID = 1L; /**
* 构造方法传入客户最大人数
*
* @param maxLineSize
*/
public CustomerLine(int maxLineSize) {
super(maxLineSize);
} /**
* 返回所有客户（服务时间）
*/
public String toString() {
if (this.size() == 0)
return "[Empty]"; StringBuilder result = new StringBuilder();
for (Customer customer : this) {
result.append(customer);
}
return result.toString();
}
} /**
* 消费者产生器
*
* @author Administrator
*
*/
class CustomerGenerator implements Runnable {
private CustomerLine customers;
private static Random rand = new Random(47); public CustomerGenerator(CustomerLine cq) {
customers = cq;
} public void run() {
try {
while (!Thread.interrupted()) {
// 每隔300MILLS就假如一个客户（来办理业务等）
TimeUnit.MILLISECONDS.sleep(rand.nextInt(300));
// 将客户加入到消费者队列
customers.put(new Customer(rand.nextInt(1000)));
// System.out.println(customers.toString());
}
} catch (InterruptedException e) {
System.out.println("CustomerGenerator interrupted");
}
System.out.println("CustomerGenerator terminating");
}
} /**
* 出纳员，业务员
*
* @author Administrator
*
*/
class Teller implements Runnable, Comparable<Teller> {
private static int counter = 0;
private final int id = counter++;// 业务员的id
private int customersServed = 0;// 已经服务的客户
private CustomerLine customers;// 客户队列
private boolean servingCustomerLine = true;// 是否正在服务客户
private int count = 0;
private boolean sort = true;// 排序方式，true为降序，false升序 public Teller(CustomerLine cq) {
customers = cq;
} @Override
public void run() {
try {
while (!Thread.interrupted()) {
// 下面两行代表正在为客户服务
Customer customer = customers.take();
count++;
TimeUnit.MILLISECONDS.sleep(customer.getServiceTime());
synchronized (this) {// 这里同步的原因是因为禁止执行到这里时线程调用doSomethingElse(),serveCustomerLine(),以及compareTo(Tellero)
customersServed++;// 服务的客户+1
while (!servingCustomerLine)
// 当出纳员去干其他的事情的时候servingCustomerLine会为false
wait();// 代表出纳员正在做其他事情
}
}
} catch (InterruptedException e) {
System.out.println(this + " interrupted");
}
System.out.println(this + " terminating");// 结束
} /**
* 出纳员做其他的事情
*/
public synchronized void doSomethingElse() {
// customersServed = 0;//服务过的客户置0
servingCustomerLine = false;
} /**
* 出纳员服务客户队列
*/
public synchronized void serveCustomerLine() {
assert !servingCustomerLine : "already serving:" + this;
servingCustomerLine = true;// 标识修改
notifyAll();// 唤醒线程
} public String toString() {
return "Teller " + id + "：" + count;
} public String shortString() {
return "T" + id;
} public int getCount() {
return count;
} public void setCount(int count) {
this.count = count;
} public boolean isSort() {
return sort;
} public void setSort(boolean sort) {
this.sort = sort;
} /**
* 优先级队列的优先级比较方法
*/
@Override
public synchronized int compareTo(Teller o) {
// TODO Auto-generated method stub
if (sort)// 降序(目的为了加入到workingTellers队列中)
return o.customersServed - customersServed > 0 ? 1
: o.customersServed - customersServed < 0 ? -1 : 0;
else
// 升序(目的为了加入到tellersDoingOtherThings队列中)
return customersServed - o.customersServed > 0 ? 1
: customersServed - o.customersServed < 0 ? -1 : 0;
} } /**
* 出纳员管理器
*
* @author Administrator
*
*/
class TellerManager implements Runnable {
private ExecutorService exec;// 执行器
private CustomerLine customers;// 客户队列
private PriorityQueue<Teller> workingTellers = new PriorityQueue<Teller>();// 降序队列
private PriorityQueue<Teller> tellersDoingOtherThings = new PriorityQueue<Teller>();// 升序队列
private int adjustmentPeriod;// 调整周期 public TellerManager(ExecutorService e, CustomerLine customers,
int adjustmentPeriod) {
exec = e;
this.customers = customers;
this.adjustmentPeriod = adjustmentPeriod;
// 构造出纳员管理器的时候默认新增一个出纳员
Teller teller = new Teller(customers);// 默认为降序
exec.execute(teller);
workingTellers.add(teller);
} /**
* 调整出纳员数量
* */
public void adjustTellerNumber() {
try {
// 利用反射调用PriorityQueue的heapify（刷新队列头）方法
Method method = workingTellers.getClass().getDeclaredMethod(
"heapify");
method.setAccessible(true);
try {
method.invoke(workingTellers);
} catch (IllegalAccessException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IllegalArgumentException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (InvocationTargetException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
} catch (NoSuchMethodException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (SecurityException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} // 如果客户队列的size大于出纳员队列的size的两倍，新增出纳员
if (customers.size() / workingTellers.size() > 2) {
if (tellersDoingOtherThings.size() > 0) {
Teller teller = tellersDoingOtherThings.remove();
teller.setSort(true);// 设置为降序
teller.serveCustomerLine();
workingTellers.add(teller);
return;
}
Teller teller = new Teller(customers);// 默认为降序
exec.execute(teller);
workingTellers.add(teller);
return;
}
// 如果出纳员的size大于1并且客户队列的size小雨出纳员size的两倍，调用一个出纳员去做其他的事情，从出纳员队列中移除
if (workingTellers.size() > 1
&& customers.size() / workingTellers.size() < 2)
reassignOneTeller();
// 如果客户队列size==0并且出纳员的size大于1，同样移除一个出纳员去做其他的事情
if (customers.size() == 0)
while (workingTellers.size() > 1)
reassignOneTeller();
} /**
* 移除一个出纳员去做其他事情
* */
private void reassignOneTeller() {
Teller teller = workingTellers.poll();
teller.setSort(false);
teller.doSomethingElse();
tellersDoingOtherThings.add(teller);
} public void run() {
try {
while (!Thread.interrupted()) {
adjustTellerNumber();
TimeUnit.MILLISECONDS.sleep(adjustmentPeriod);
// 打印客户和出纳员队列
System.out.print("customers[" + customers
+ "] workingTellers[");
for (Teller teller : workingTellers) {
System.out.print(teller.shortString() + ":"
+ teller.getCount() + " ");
}
// 打印在做其他事情的出纳员队列
System.out.print("] doingOtherThingTellers[");
for (Teller teller : tellersDoingOtherThings) {
System.out.print(teller.shortString() + ":"
+ teller.getCount() + " ");
}
if (tellersDoingOtherThings.size() == 0)
System.out.print("Empty");
System.out.println("]\n");
}
} catch (InterruptedException e) {
System.out.println(this + " interrupted");
}
System.out.println(this + " terminating");
} public String toString() {
return "TellerManager";
}
} public class BankTellerSimulation {
static final int MAX_LINE_SIZE = 50;
static final int ADJUSTMENT_PERIOD = 1000; public static void main(String[] args) throws Exception {
ExecutorService exec = Executors.newCachedThreadPool();
CustomerLine customers = new CustomerLine(MAX_LINE_SIZE);
exec.execute(new CustomerGenerator(customers));
exec.execute(new TellerManager(exec, customers, ADJUSTMENT_PERIOD));
if (args.length > 0)
TimeUnit.SECONDS.sleep(new Integer(args[0]));
else {
System.out.println("Press 'Enter' to quit");
System.in.read();
}
exec.shutdownNow();
}
}
代码中注释唯一需要注意的地方是：
try {
// 利用反射调用PriorityQueue的heapify（刷新队列头）方法
Method method = workingTellers.getClass().getDeclaredMethod(
"heapify");
method.setAccessible(true);
try {
method.invoke(workingTellers);
} catch (IllegalAccessException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IllegalArgumentException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (InvocationTargetException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
} catch (NoSuchMethodException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (SecurityException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}这个地方可以看出PriorityQueue的设计还是可以完善的，如果PriorityQueue中的队列元素是线程，线程内部需要调整比较因子，那么PriorityQueue没有提供出一个可以刷新队列头的方法的，如果在此demo中不刷新队列头而部分线程（出纳员）服务人数增长过快超过当前队列头的服务人数，则正在服务的队列的排序会造成假象。而heapify这个方法正是刷新队列头的方法可以却没有公开出来，无奈只有通过反射来调用刷新队列头，此处也可以看出reflect机制在JAVA中的强大。
如有错误还请提出指正。