Lock可以替换synchronized.
上面用来做为锁对象的SaleWindow.class没有别的操作,而且获取锁和释放锁都是在内部隐藏完成的.
Java的思想是万物皆对象,我们把这种锁也描述成为一个对象,就是Lock.....
Lock中的lock和unlock显式的打开和关闭(可视化)更直观.
Lock实现提供了比使用synchronized方法和语句可获得的更广泛的锁定操作.
此实现允许更灵活的结构,可以具有差别很大的属性,可以支持多个相关的Condition对象.
Lock可以替换synchronized.
使用synchronized
synchronized(SaleWindow.class) {
}
SaleWindow.class 这个锁对象没有别的操作,而且这个锁对象获取锁和释放锁的操作都是在内部隐藏的完成的,而Java的思想是万物皆对象.
我们把这种锁也描述成了一个对象,这个对象就是Lock.
Lock中获取锁和释放锁都提供了对应的方法,这两种操作都是一种显式的操作,更直观的表示了这个问题.
如果仅仅把之间的synchronized替换成Lock运行是会报错的.
原因就是锁替换了synchronized 但是wait只能在同步中调用.
我们应该把wait 和 notify 等待唤醒机制都替换掉.
上面说的Condition是将Object监视器方法(wait,notify和notifyAll)分解成截然不同的对象,以便通过这些对象与任意Lock实现组合使用,为每个对象提供多个等待...其中Lock替代了synchronized方法和语句的使用,Condition替代了Object监视器方法的使用.
Condition中有await() signal() 和 signalAll().....
SaleWindow.java
1 import java.util.List; 2 import java.util.Random; 3 import java.util.concurrent.TimeUnit; 4 import java.util.concurrent.locks.Condition; 5 import java.util.concurrent.locks.Lock; 6 7 public class SaleWindow implements Runnable { 8 9 private List<Food> foods; 10 11 public List<Food> getFoods() { 12 return foods; 13 } 14 15 public void setFoods(List<Food> foods) { 16 this.foods = foods; 17 } 18 19 public SaleWindow(List<Food> foods) { 20 this.foods = foods; 21 } 22 23 public SaleWindow() { 24 } 25 26 public void sale() { 27 while (true) { 28 // 加锁 29 Lock lock = MyLock.LOCK; 30 Condition cook_con = MyLock.COOK_CON; 31 Condition sale_con = MyLock.SALE_CON; 32 lock.lock(); 33 if (foods.size() > 0) { 34 try { 35 Food food = foods.get(0); 36 System.out.println(Thread.currentThread().getName() 37 + ": 卖出了 " + food.getId() + " 号饭..."); 38 Random ran = new Random(); 39 int i = ran.nextInt(300); 40 41 TimeUnit.MILLISECONDS.sleep(i); 42 foods.remove(0); 43 // SaleWindow.class.notify();//随机唤醒一条等待的线程 44 cook_con.signal(); 45 } catch (InterruptedException e) { 46 e.printStackTrace(); 47 } 48 } else { 49 System.out.println(Thread.currentThread().getName() 50 + ":饭买完了。厨师赶紧做，我休息了。。。"); 51 try { 52 sale_con.await(); 53 } catch (InterruptedException e) { 54 e.printStackTrace(); 55 } 56 57 } 58 // 释放锁 59 lock.unlock(); 60 } 61 } 62 63 @Override 64 public void run() { 65 sale(); 66 } 67 68 }
Cook.java
1 import java.util.List; 2 import java.util.Random; 3 import java.util.concurrent.TimeUnit; 4 import java.util.concurrent.locks.Condition; 5 import java.util.concurrent.locks.Lock; 6 7 public class Cook implements Runnable { 8 9 private List<Food> foods; 10 private static int num = 1; 11 private static final int MAXSIZE = 1; 12 13 public List<Food> getFoods() { 14 return foods; 15 } 16 17 public void setFoods(List<Food> foods) { 18 this.foods = foods; 19 } 20 21 public Cook(List<Food> foods) { 22 this.foods = foods; 23 } 24 25 public Cook() { 26 } 27 28 public void produce() { 29 while (true) { 30 Lock lock = MyLock.LOCK; 31 Condition cook_con = MyLock.COOK_CON; 32 Condition sale_con = MyLock.SALE_CON; 33 lock.lock(); 34 if (foods.size() < MAXSIZE) { 35 Food food = new Food((num++) + ""); 36 foods.add(food); 37 System.out.println(Thread.currentThread().getName() + " ：做好 " 38 + food.getId() + " 号饭了"); 39 Random ran = new Random(); 40 int i = ran.nextInt(300); 41 try { 42 TimeUnit.MILLISECONDS.sleep(i); 43 } catch (InterruptedException e) { 44 e.printStackTrace(); 45 } 46 47 // SaleWindow.class.notify(); 48 49 sale_con.signal();//唤醒等待中的一条线程 50 } else { 51 System.out.println(Thread.currentThread().getName() 52 + " :桌子放满了。窗口赶紧卖，我休息了。。。"); 53 54 try { 55 cook_con.await(); 56 } catch (InterruptedException e) { 57 e.printStackTrace(); 58 } 59 } 60 lock.unlock(); 61 } 62 63 } 64 65 @Override 66 public void run() { 67 produce(); 68 } 69 }
Food.java
1 public class Food { 2 3 private String id; 4 5 6 public Food(String id) { 7 this.id = id; 8 } 9 10 public String getId() { 11 return id; 12 } 13 14 public void setId(String id) { 15 this.id = id; 16 } 17 18 19 }
MyLock.java
1 import java.util.concurrent.locks.Condition; 2 import java.util.concurrent.locks.Lock; 3 import java.util.concurrent.locks.ReentrantLock; 4 //把锁抽取出来. 5 public class MyLock { 6 7 public static final Lock LOCK = new ReentrantLock(true);//公平模式 8 public static final Condition COOK_CON = LOCK.newCondition();//监视Cook的监视器 9 public static final Condition SALE_CON = LOCK.newCondition();//监视Sale的监视器 10 //两个监视器之间可以相互通知 本方唤醒对方的等待中的一条线程. 11 12 //构造方法私有 单例 饿汉式 13 private MyLock(){} 14 }
Test.java
1 import java.util.ArrayList; 2 import java.util.List; 3 4 public class Test { 5 6 public static void main(String[] args) { 7 8 /*List<Food> foods = new ArrayList<Food>(); 9 for (int i = 0; i < 10; i++) { 10 foods.add(new Food((i+1)+"")); 11 } 12 Restaurant r = new Restaurant(foods); 13 for (int i = 0; i < 3; i++) { 14 new Thread(r).start(); 15 }*/ 16 List<Food> foods = new ArrayList<Food>(); 17 for (int i = 0; i < 4; i++) { 18 new Thread(new Cook(foods),"Cook"+(i+1)).start(); 19 } 20 for (int i = 0; i < 3; i++) { 21 new Thread(new SaleWindow(foods),"sale"+(i+1)).start(); 22 } 23 } 24 }
本文转自SummerChill博客园博客，原文链接：http://www.cnblogs.com/DreamDrive/p/6204665.html，如需转载请自行联系原作者
