Java:多线程模拟多站点售票过程-阿里云开发者社区

Java:多线程模拟多站点售票过程

2017-11-15 1213

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简介：

这是一个在并发状态下对共享资源的多线程访问。这些访问必须是互斥的进行，因为涉及到对资源的修改。假设现在销售火车票。目的地有 3 个，分别是北京，天津和上海。使用一个枚举类型表示。

Destation.java

package com.zj.tickets;

public enum Destation {

BEIJING , SHANGHAI , TIANJING

}

下面设计车票类， final int original 表示车票基数； int current 表示当前还有多少张票； Destation destation 表示目的地，它必须从上面的枚举型中取出其一。

Ticket.java

package com.zj.tickets;

public class Ticket {

private final int original ;

private int current ;

private final Destation destation ;

public Ticket( int nums, Destation where) {

current = original = nums;

destation = where;

}

public int degress() {

return -- current ;

}

public int original() {

return original ;

}

public boolean soldout() {

return current <= 0;

}

public Destation getDestation() {

return destation ;

}

public int getCurrent() {

return current ;

}

下面设计售票厅类， Map<Destation, Ticket> tickets 表示目前可销售的车票种类，它通过一个 static 块初始化。 Map<Destation, Integer> records 是当前售票厅的火车票销售情况。 List<BookingOffice> offices 表示当前可工作的所有售票厅，每个售票厅是一个线程。 int ticketsSold 表示当前售票厅售出的火车票总数。 int id 表示当前售票厅编号。

每个线程都会模拟客户买票、工作人员查询数据库和售票交易过程。

模拟的数据为，当前发往北京、上海和天津的火车票各 5 张；每个售票厅交易 5 次（无论交易成功或失败）后关闭。

BookingOffice.java

package com.zj.tickets;

import java.util.ArrayList;

import java.util.HashMap;

import java.util.List;

import java.util.Map;

import java.util.Random;

import java.util.concurrent.TimeUnit;

public class BookingOffice implements Runnable {

private static Map<Destation, Ticket> tickets = new HashMap<Destation, Ticket>();

private Map<Destation, Integer> records ;

private static List<BookingOffice> offices = new ArrayList<BookingOffice>();

private int ticketsSold = 0;

private final int id ;

// now today's tickets for sell:

static {

tickets .put(Destation. BEIJING , new Ticket(5, Destation. BEIJING ));

tickets .put(Destation. SHANGHAI , new Ticket(5, Destation. SHANGHAI ));

tickets .put(Destation. TIANJING , new Ticket(5, Destation. TIANJING ));

}

public BookingOffice( int id) {

this . id = id;

offices .add( this );

resetRecords();

}

private void resetRecords() {

records = new HashMap<Destation, Integer>();

}

private void addRecords(Destation d) {

Integer freq = records .get(d);

records .put(d, freq == null ? 1 : freq + 1);

}

public void run() {

int transaction = 5;

while (transaction-- > 0) {

// simulate a customer's coming:

Destation d = Destation.values()[ new Random().nextInt(Destation

.values(). length )];

print( this + "i want a ticket for " + d);

// simulate the officer's checking:

try {

TimeUnit. SECONDS .sleep(1);

} catch (InterruptedException e) {

e.printStackTrace();

}

// simulate the transaction:

Ticket wanted = tickets .get(d);

synchronized ( wanted ) {

if (!wanted.soldout()) {

print( this + "sold a ticket for " + d);

wanted.degress();

addRecords(d);

++ ticketsSold ;

print( this + "" + d + " tickets still have "

+ wanted.getCurrent());

} else

print( this + "tickets for " + d + " have been sold out." );

}

print( this + "closed" );

print( this + "totally sold tickets:" + ticketsSold + ",sell records:"

+ records );

}

public synchronized int getValue() {

return ticketsSold ;

}

public String toString() {

return "<Officce-" + id + ">" ;

}

static void print(String s) {

System. out .println(s);

}

模拟售票过程如下，启动 5 个售票厅。

Sell.java

package com.zj.tickets;

import java.util.concurrent.ExecutorService;

import java.util.concurrent.Executors;

public class Sell {

public static void main(String[] args) throws Exception {

ExecutorService exec = Executors.newCachedThreadPool();

for ( int i = 0; i < 5; i++)

exec.execute( new BookingOffice(i));

exec.shutdown();

}

结果：

<Officce-0>i want a ticket for BEIJING

<Officce-1>i want a ticket for SHANGHAI

<Officce-2>i want a ticket for TIANJING

<Officce-3>i want a ticket for SHANGHAI

<Officce-4>i want a ticket for SHANGHAI

<Officce-0>sold a ticket for BEIJING

<Officce-0>BEIJING tickets still have 4

<Officce-0>i want a ticket for TIANJING

<Officce-1>sold a ticket for SHANGHAI

<Officce-1>SHANGHAI tickets still have 4

<Officce-1>i want a ticket for SHANGHAI

<Officce-2>sold a ticket for TIANJING

<Officce-2>TIANJING tickets still have 4

<Officce-2>i want a ticket for BEIJING

<Officce-3>sold a ticket for SHANGHAI

<Officce-3>SHANGHAI tickets still have 3

<Officce-3>i want a ticket for TIANJING

<Officce-4>sold a ticket for SHANGHAI

<Officce-4>SHANGHAI tickets still have 2

<Officce-4>i want a ticket for BEIJING

<Officce-4>sold a ticket for BEIJING

<Officce-4>BEIJING tickets still have 3

<Officce-4>i want a ticket for SHANGHAI

<Officce-3>sold a ticket for TIANJING

<Officce-3>TIANJING tickets still have 3

<Officce-3>i want a ticket for TIANJING

<Officce-2>sold a ticket for BEIJING

<Officce-2>BEIJING tickets still have 2

<Officce-2>i want a ticket for BEIJING

<Officce-1>sold a ticket for SHANGHAI

<Officce-1>SHANGHAI tickets still have 1

<Officce-1>i want a ticket for SHANGHAI

<Officce-0>sold a ticket for TIANJING

<Officce-0>TIANJING tickets still have 2

<Officce-0>i want a ticket for SHANGHAI

<Officce-4>sold a ticket for SHANGHAI

<Officce-4>SHANGHAI tickets still have 0

<Officce-4>i want a ticket for BEIJING

<Officce-3>sold a ticket for TIANJING

<Officce-3>TIANJING tickets still have 1

<Officce-3>i want a ticket for BEIJING

<Officce-2>sold a ticket for BEIJING

<Officce-2>BEIJING tickets still have 1

<Officce-2>i want a ticket for SHANGHAI

<Officce-1>tickets for SHANGHAI have been sold out.

<Officce-1>i want a ticket for SHANGHAI

<Officce-0>tickets for SHANGHAI have been sold out.

<Officce-0>i want a ticket for SHANGHAI

<Officce-4>sold a ticket for BEIJING

<Officce-4>BEIJING tickets still have 0

<Officce-4>i want a ticket for BEIJING

<Officce-3>tickets for BEIJING have been sold out.

<Officce-3>i want a ticket for BEIJING

<Officce-2>tickets for SHANGHAI have been sold out.

<Officce-2>i want a ticket for SHANGHAI

<Officce-1>tickets for SHANGHAI have been sold out.

<Officce-1>i want a ticket for BEIJING

<Officce-0>tickets for SHANGHAI have been sold out.

<Officce-0>i want a ticket for SHANGHAI

<Officce-4>tickets for BEIJING have been sold out.

<Officce-4>closed

<Officce-4>totally sold tickets:4,sell records:{BEIJING=2, SHANGHAI=2}

<Officce-3>tickets for BEIJING have been sold out.

<Officce-3>closed

<Officce-3>totally sold tickets:3,sell records:{TIANJING=2, SHANGHAI=1}

<Officce-2>tickets for SHANGHAI have been sold out.

<Officce-2>closed

<Officce-2>totally sold tickets:3,sell records:{BEIJING=2, TIANJING=1}

<Officce-1>tickets for BEIJING have been sold out.

<Officce-1>closed

<Officce-1>totally sold tickets:2,sell records:{SHANGHAI=2}

<Officce-0>tickets for SHANGHAI have been sold out.

<Officce-0>closed

<Officce-0>totally sold tickets:2,sell records:{BEIJING=1, TIANJING=1}

本文转自zhangjunhd51CTO博客，原文链接：http://blog.51cto.com/zhangjunhd/70767，如需转载请自行联系原作者

Java:多线程模拟多站点售票过程

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