Java多线程之银行出纳员仿真

package concurrent;

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;

class Customer {
    private final int serviceTime;

    public Customer(int tm) {
        serviceTime = tm;
    }

    public int getServiceTime() {
        return serviceTime;
    }

    public String toString() {
        return "[" + serviceTime + "]";
    }
}

class CustomerLine extends ArrayBlockingQueue<Customer> {
    public CustomerLine(int maxLineSize) {
        super(maxLineSize);
    }

    public String toString() {
        if (this.size() == 0)
            return "[Empty]";
        
        StringBuilder result = new StringBuilder();
        for (Customer customer : this) {
            result.append(customer);
        }
        return result.toString();
    }
}

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()) {
                TimeUnit.MILLISECONDS.sleep(rand.nextInt(300));
                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");
    }
}

class Teller implements Runnable, Comparable<Teller> {
    private static int counter = 0;
    private final int id = counter++;
    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

    public Teller(CustomerLine cq) {
        customers = cq;
    }

    @Override
    public void run() {
        try {
            while (!Thread.interrupted()) {
                Customer customer = customers.take();
                TimeUnit.MILLISECONDS.sleep(customer.getServiceTime());
                synchronized (this) {
                    customersServed++;
                    while (!servingCustomerLine)
                        wait();
                }
            }
        } catch (InterruptedException e) {
            System.out.println(this + " interrupted");
        }
        System.out.println(this + " terminating");// 结束
    }

    public synchronized void doSomethingElse() {
        customersServed = 0;
        servingCustomerLine = false;
    }

    public synchronized void serveCustomerLine() {
        assert !servingCustomerLine : "already serving:" + this;
        servingCustomerLine = true;
        notifyAll();
    }

    public String toString() {
        return "Teller " + id + " ";
    }

    public String shortString() {
        return "T" + id;
    }

    public synchronized int compareTo(Teller other) {
        return customersServed < other.customersServed ? -1
                : (customersServed == other.customersServed ? 0 : 1);
    }
}

class TellerManager implements Runnable {
    private ExecutorService exec;
    private CustomerLine customers;
    private PriorityQueue<Teller> workingTellers = new PriorityQueue<Teller>();
    private Queue<Teller> tellersDoingOtherThings = new LinkedList<Teller>();
    private int adjustmentPeriod;
    private static Random rand = new Random(47);

    public TellerManager(ExecutorService e, CustomerLine customers,
            int adjustmentPeriod) {
        exec = e;
        this.customers = customers;
        this.adjustmentPeriod = adjustmentPeriod;
        Teller teller = new Teller(customers);
        exec.execute(teller);
        workingTellers.add(teller);
    }

    /**
     * 调整出纳员数量
     * */
    public void adjustTellerNumber() {
        if (customers.size() / workingTellers.size() > 2) {
            if (tellersDoingOtherThings.size() > 0) {
                Teller teller = tellersDoingOtherThings.remove();
                teller.serveCustomerLine();
                workingTellers.offer(teller);
                return;
            }
            Teller teller = new Teller(customers);
            exec.execute(teller);
            workingTellers.add(teller);
            return;
        }
        if (workingTellers.size() > 1
                && customers.size() / workingTellers.size() < 2)
            reassignOneTeller();

        if (customers.size() == 0)
            while (workingTellers.size() > 1)
                reassignOneTeller();
    }

    /**
     * 分配一个出纳员
     * */
    private void reassignOneTeller() {
        Teller teller = workingTellers.poll();
        teller.doSomethingElse();
        tellersDoingOtherThings.offer(teller);
    }

    public void run() {
        try {
            while (!Thread.interrupted()) {
                TimeUnit.MILLISECONDS.sleep(adjustmentPeriod);
                adjustTellerNumber();
                System.out.print(customers + "{");
                for (Teller teller : workingTellers) {
                    System.out.print(teller.shortString() + " ");
                }
                System.out.println("}");
            }
        } 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();
    }
}