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 9private List<Food> foods;10 11public List<Food> getFoods() {12 return foods;13}14 15public void setFoods(List<Food> foods) {16 this.foods = foods;17}18 19public SaleWindow(List<Food> foods) {20 this.foods = foods;21}22 23public SaleWindow() {24}25 26public 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@Override64public 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 9private List<Food> foods;10private static int num = 1;11private static final int MAXSIZE = 1;12 13public List<Food> getFoods() {14 return foods;15}16 17public void setFoods(List<Food> foods) {18 this.foods = foods;19}20 21public Cook(List<Food> foods) {22 this.foods = foods;23}24 25public Cook() {26}27 28public 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@Override66public void run() {67 produce();68}69 }
Food.java
1 public class Food { 2 3private String id; 4 56public Food(String id) { 7 this.id = id; 8} 9 10public String getId() {11 return id;12}13 14public void setId(String id) {15 this.id = id;16}171819 }
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 { 67public static final Lock LOCK = new ReentrantLock(true);//公平模式 8public static final Condition COOK_CON = LOCK.newCondition();//监视Cook的监视器 9public 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.1112//构造方法私有 单例 饿汉式13private MyLock(){}14 }
Test.java
1 import java.util.ArrayList; 2 import java.util.List; 3 4 public class Test { 5 6public static void main(String[] args) { 78 /*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 }
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