Java多线程之~~~synchronized添加参数来实现独立的代码片段

有时候我们并不想在整个方法前面加上synchronized这个关键字，这样会使整个方法调用变的缓慢，我们只在关键
代码的地方增加这个synchronized这个关键字，然后这样就能加快方法或者代码的执行效率。然后可能还有一种情况就
是，我们有两个变量，其中任何一个变量都是同时只能一个变量访问，但是两个变量可以在同时被两个变量访问，这种
需求下我们就得使用sychronized的带参数的方法来实现这种需求。

下面我们来看一个例子，一个模拟电影院售票的例子
[java] view plain copy print?
package com.bird.concursey.charpet2;

public class Cinema {

private long vacanciesCinema1;  private long vacanciesCinema2;  private final Object controlCinema1 = new Object();  private final Object controlCinema2 = new Object();  public Cinema() {      vacanciesCinema1 = 20;      vacanciesCinema2 = 20;  }  public boolean sellTickets1(int number) {      synchronized (controlCinema1) {          if(number < vacanciesCinema1) {              vacanciesCinema1 -= number;              return true;          }else{              return false;          }      }  }  public boolean sellTickets2(int number) {      synchronized (controlCinema2) {          if(number < vacanciesCinema2) {              vacanciesCinema2 -= number;              return true;          }else{              return false;          }      }  }  public boolean returnTicket1(int number) {      synchronized (controlCinema1) {          vacanciesCinema1 += number;          return true;      }  }  public boolean returnTicket2(int number) {      synchronized (controlCinema2) {          vacanciesCinema2 += number;          return true;      }  }  public long getVacanciesCinema1() {      return vacanciesCinema1;  }  public void setVacanciesCinema1(long vacanciesCinema1) {      this.vacanciesCinema1 = vacanciesCinema1;  }  public long getVacanciesCinema2() {      return vacanciesCinema2;  }  public void setVacanciesCinema2(long vacanciesCinema2) {      this.vacanciesCinema2 = vacanciesCinema2;  }  

}

下面是实际售票的类

[java] view plain copy print?
package com.bird.concursey.charpet2;

public class TicketOffice1 implements Runnable {

private Cinema cinema;  public TicketOffice1(Cinema cinema) {      this.cinema = cinema;  }  @Override  public void run() {      cinema.sellTickets1(3);      cinema.sellTickets1(2);      cinema.sellTickets2(2);      cinema.returnTicket1(3);      cinema.sellTickets1(5);      cinema.sellTickets2(2);      cinema.sellTickets2(2);      cinema.sellTickets2(2);  }  

}

[java] view plain copy print?
package com.bird.concursey.charpet2;

public class TicketOffice2 implements Runnable {

private Cinema cinema;  public TicketOffice2(Cinema cinema) {      this.cinema = cinema;  }  @Override  public void run() {      cinema.sellTickets2(2);      cinema.sellTickets2(4);      cinema.sellTickets1(2);      cinema.sellTickets1(1);      cinema.returnTicket2(2);      cinema.sellTickets1(3);      cinema.sellTickets2(2);      cinema.sellTickets1(2);  }  public static void main(String[] args) {      Cinema cinema = new Cinema();      TicketOffice1 ticketOffice1 = new TicketOffice1(cinema);      Thread thread1 = new Thread(ticketOffice1, "TicketOffice1");      TicketOffice2 ticketOffice2 = new TicketOffice2(cinema);      Thread thread2 = new Thread(ticketOffice2, "TicketOffice2");      thread1.start();      thread2.start();      try {          thread1.join();          thread2.join();      } catch (InterruptedException e) {          e.printStackTrace();      }      System.out.printf("Room 1 Vacancies: %d\n",cinema.getVacanciesCinema1());      System.out.printf("Room 2 Vacancies: %d\n",cinema.getVacanciesCinema2());  }  

}

这里可以看到，每次运行都会是期望的效果，而且通过单例模式，我们很好的控制了两个属性的访问顺序，很好的实
现了我们的需求。