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
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
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); }}
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。
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