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

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。