我是 Java 新手，并试图了解同步的工作原理。所以我创建了一个飞机预订系统，我能够模拟多个用户尝试进行预订并使用同步来获得正确的输出。
现在它起作用了，我在想它在现实世界中是如何起作用的。例如，假设应用程序是基于 Swing 构建的，这是一个多用户应用程序。为简单起见，我们假设只有两个平面“AAA”和“BBB”。该应用程序可以安装在每个售票柜台代理的计算机、机场的售货亭以及不同旅行社的计算机中，并且它们都访问相同的数据库。
在这种情况下，每个用户/计算机将有自己的 Reserve 类、Transaction 类和 Plane 类的实例。所以 Transaction 类中只有一个线程/请求，并且没有同步。
我的问题是，如何实际设计/实施像这样的预订系统这样的多用户应用程序，以便所有用户都访问 Transacion 类的一个实例，以便发生同步。您也可以将这个问题视为，我如何构建一个由不同玩家在不同计算机上玩的多用户游戏。另一个例子是当应用程序在 ATM 和柜员机上运行时进行存款、取款和转账的银行系统。
///////////////////////////
Reserve.java ---> 用户提出的每个请求的入口点
/////////////////////////
import java.io.IOException;
public class Reserve {
static int queryseatsavailableinx;
static int queryseatsavailableiny;
static
{
seats s = null;
try {
s = new seats();
} catch (IOException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
}
try {
queryseatsavailableinx = s.getseatsinplanex("AAA");
queryseatsavailableiny = s.getseatsinplanex("BBB");
} catch (IOException e) {
e.printStackTrace();
}
}
static final Plane x1 = new Plane("AAA", 001, queryseatsavailableinx );
static final Plane y1 = new Plane("BBB", 002, queryseatsavailableiny);
static final Transaction trans = new Transaction();
public static void main(String[] args) throws InterruptedException {
Thread t1 = new Thread(new Runnable() {
public void run() {
trans.getPlaneInfo(x1);
}
});
Thread t2 = new Thread(new Runnable() {
public void run() {
//trans.getPlaneInfo(x1);
trans.reserveSeats(x1,3);
}
});
Thread t3 = new Thread(new Runnable() {
public void run() {
//trans.getPlaneInfo(y1);
trans.reserveSeats(y1,8);
}
});
Thread t4 = new Thread(new Runnable() {
public void run() {
//trans.getPlaneInfo(x1);
trans.reserveSeats(x1,2);
}
});
t1.start();
t2.start();
t3.start();
t4.start();
t1.join();
t2.join();
t3.join();
t4.join();
}
}
///////////////////////////
Transaction.java ---> 实际事务发生在这里
/////////////////////////
public class Transaction {
public void getPlaneInfo(Plane x){
synchronized(this){
int number = x.getSeatCapacity();
String planename=x.getPlaneName();
System.out.printf("The number of seats in plane %s is %d\n",planename,number);
}
}
public void reserveSeats(Plane x, int seatstobereserved) {
synchronized(this){
x.updateSeatCapacity(seatstobereserved);
}
}
}
///////////////////////////
Plane.java ---> 飞机信息
/////////////////////////
final public class Plane {
private String planename = null;
private int planeid = 0;
private int availableseatcapacity = 0;
Plane(String planename, int planeid, int seatcapacity) {
this.planename = planename;
this.planeid = planeid;
this.availableseatcapacity = seatcapacity;
}
public String getPlaneName() {
return planename;
}
public int getPlaneId() {
return planeid;
}
public int getSeatCapacity() {
return availableseatcapacity;
}
public void updateSeatCapacity(int reservedseats) {
availableseatcapacity -= reservedseats;
System.out.printf("\n%d Seats successfully reserved and remaining seats " +
"in the plane %s are %d\n",reservedseats, planename,availableseatcapacity);
}
}
///////////////////////////
Seats.java ---> 为了模拟用户每次发出请求，从公共数据源/数据库中检索“可用座位数”。/////////////////////////
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.EOFException;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
final public class seats {
seats() throws IOException {
DataOutputStream di1 = new DataOutputStream(new FileOutputStream(
"\\PlaneReservation\\bin\\a.bin"));
DataOutputStream di2 = new DataOutputStream(new FileOutputStream(
"\\PlaneReservation\\bin\\b.bin"));
di1.writeInt(300);
di2.writeInt(200);
di1.flush();
di2.flush();
di1.close();
di2.close();
}
public int getseatsinplanex(String s) throws IOException {
if (s.equals("AAA")) {
FileInputStream fis1 = new FileInputStream("\\PlaneReservation\\bin\\a.bin");
DataInputStream dis1 = new DataInputStream(fis1);
int number = 0;
boolean eof = false;
while (!eof) {
try {
number = dis1.readInt();
// System.out.println(number);
} catch (EOFException eofx) {
eof = true;
dis1.close();
}
}
return number;
} else if (s.equals("BBB")) {
FileInputStream fis2 = new FileInputStream("\\PlaneReservation\\bin\\b.bin");
DataInputStream dis2 = new DataInputStream(fis2);
int number = 0;
boolean eof = false;
while (!eof) {
try {
number = dis2.readInt();
//System.out.println(number);
} catch (EOFException eofx) {
eof = true;
dis2.close();
}
}
return number;
}
return 0;
}
}