赵雅智_java 多线程（三）之线程间的通信

赵雅智_java 多线程（3）之线程间的通信

线程间的通信

两个或两个以上的线程处理同一个资源，处理的动作是不一样的。

这样就需要将不同的动作代码放到不同的run方法中，run方法要封装到单独的类中。

使用方法：

同步中使用object类的方法

wait()：让当前线程处于等待状态，释放cpu资源，同时释放锁。
notify()：唤醒等待的线程，唤醒第一个
notifyAll()：唤醒所以等待的线程。

 

实例，生产者和消费者。

分析：

生产者-消费者问题是多线程同步处理的典型问题

有一块生产者和消费者共享的有界缓冲区，生产者往缓冲区放入产品，消费者从缓冲区取走产品这个过程可以无休止的执行，不能因缓冲区满生产者放不进产品而终止，也不能因缓冲区空消费者无产品可取而终止。

线程B写一次，线程A读一次在某个时候线程B运行速度比较快，在线程A未读取上一个数据之前，B就写了第二次数据，造成数据遗漏。在某个时候线程A运行速度比较快，它读完一次数据之后，线程B还没来得及写，线程A又来读第二次。结果线程A读不到数据，导致运行出错。线程B正在写数据时，线程A也来读取数据，这时可能线程B还没将数据写完，线程A将数据读走，导致程序出错。

1.搭架子

package com.csdn;public class ProAndSell {/** * @param args */public static void main(String[] args) {// TODO Auto-generated method stub}}//资源类class Resource{String name;String sex;}//生产类class Product implements Runnable{@Overridepublic void run() {// TODO Auto-generated method stub}}//销售类 class Sell implements Runnable{@Overridepublic void run() {// TODO Auto-generated method stub}}

2.填充代码

package com.csdn;public class ProAndSell {/** * @param args */public static void main(String[] args) {// TODO Auto-generated method stubResource r = new Resource();Product pro = new Product(r);Sell se = new Sell(r);Thread t1 = new Thread(pro);Thread t2 = new Thread(se);t1.start();t2.start();}}//资源类class Resource{String name;String sex;}//生产类class Product implements Runnable{private Resource r;public Product(Resource r){this.r = r;}@Overridepublic void run() {int x = 0;while(true){if(x == 0){r.name = "张三";r.sex = "男";} else {r.name = "lisi";r.sex = "nv";}x=(x+1)%2;}}}//销售类 class Sell implements Runnable{private Resource r;public Sell(Resource r){this.r = r;}@Overridepublic void run() {while(true){System.out.println(r.name+"...."+r.sex);}}}

两个线程，首先输入的线程生产出张三,男，CPU资源没有切换给输出线程，输入还拥有CPU资源，接着生产，生产张三，CPU资源切换给输出，出现张三.......nv

3.封锁，同步代码块

package com.csdn;public class ProAndSell {/** * @param args */public static void main(String[] args) {// TODO Auto-generated method stubResource r = new Resource();Product pro = new Product(r);Sell se = new Sell(r);Thread t1 = new Thread(pro);Thread t2 = new Thread(se);t1.start();t2.start();}}//资源类class Resource{String name;String sex;}//生产类class Product implements Runnable{private Resource r;Object obj = new Object();public Product(Resource r){this.r = r;}@Overridepublic void run() {int x = 0;while(true){synchronized (obj) {if(x == 0){r.name = "张三";r.sex = "男";} else {r.name = "lisi";r.sex = "nv";}}x=(x+1)%2;}}}//销售类 class Sell implements Runnable{private Resource r;Object obj = new Object();public Sell(Resource r){this.r = r;}@Overridepublic void run() {while(true){synchronized (obj) {System.out.println(r.name+"...."+r.sex);}}}}

还是有错误，是以为上锁的时候是两把锁

4.让生产者和消费者有共同的锁

package com.csdn;public class ProAndSell {/** * @param args */public static void main(String[] args) {// TODO Auto-generated method stubResource r = new Resource();Product pro = new Product(r);Sell se = new Sell(r);Thread t1 = new Thread(pro);Thread t2 = new Thread(se);t1.start();t2.start();}}//资源类class Resource{String name;String sex;}//生产类class Product implements Runnable{private Resource r;public Product(Resource r){this.r = r;}@Overridepublic void run() {int x = 0;while(true){synchronized (r) {if(x == 0){r.name = "张三";r.sex = "男";} else {r.name = "lisi";r.sex = "nv";}}x=(x+1)%2;}}}//销售类 class Sell implements Runnable{private Resource r;public Sell(Resource r){this.r = r;}@Overridepublic void run() {while(true){synchronized (r) {System.out.println(r.name+"...."+r.sex);}}}}

线程的随机性

5.线程的通信

package com.csdn;public class ProAndSell {public static void main(String[] args) {// TODO Auto-generated method stubResource r = new Resource();Product pro = new Product(r);Sell se = new Sell(r);Thread t1 = new Thread(pro);Thread t2 = new Thread(se);t1.start();t2.start();}}//资源类class Resource{String name;String sex;boolean f;}//生产类class Product implements Runnable{private Resource r;public Product(Resource r){this.r = r;}@Overridepublic void run() {int x = 0;while(true){synchronized (r) {if(r.f)try {r.wait();} catch (InterruptedException e) {// TODO Auto-generated catch blocke.printStackTrace();}if(x == 0){r.name = "张三";r.sex = "男";} else {r.name = "lisi";r.sex = "nv";}r.f = true;r.notify();}x=(x+1)%2;}}}//销售类 class Sell implements Runnable{private Resource r;public Sell(Resource r){this.r = r;}@Overridepublic void run() {while(true){synchronized (r) {if(!r.f)try {r.wait();} catch (InterruptedException e) {// TODO Auto-generated catch blocke.printStackTrace();}System.out.println(r.name+"...."+r.sex);r.f = false;r.notify();}}}}

6.优化代码

package com.csdn;public class ProAndSell {public static void main(String[] args) {// TODO Auto-generated method stubResource r = new Resource();Product pro = new Product(r);Sell se = new Sell(r);Thread t1 = new Thread(pro);Thread t2 = new Thread(se);t1.start();t2.start();}}//资源类class Resource{private String name;private String sex;private boolean f;public synchronized void set(String name, String sex){if(f)try {wait();} catch (InterruptedException e) {// TODO Auto-generated catch blocke.printStackTrace();}this.name = name;this.sex = sex;f=true;notify();}public synchronized void out(){if(!f)try {wait();} catch (InterruptedException e) {// TODO Auto-generated catch blocke.printStackTrace();}System.out.println(name+"...."+sex);f = false;notify();}}//生产类class Product implements Runnable{private Resource r;public Product(Resource r){this.r = r;}@Overridepublic void run() {int x = 0;while(true){if(x == 0){r.set("张三", "男");} else {r.set("lisi", "nv");}x=(x+1)%2;}}}//销售类 class Sell implements Runnable{private Resource r;public Sell(Resource r){this.r = r;}@Overridepublic void run() {while(true){r.out();}}}

三段代码并行

package com.csdn;public class ThreadDemo6 {/** * @param args */public static void main(String[] args) {new Thread(){public void run(){for(int i=0;i<100;i++){System.out.println("a="+i);}}}.start();for(int i=0;i<100;i++){System.out.println("b="+i);}Runnable r=new Runnable(){@Overridepublic void run() {for(int i=0;i<100;i++){System.out.println("c="+i);}}};new Thread(r).start();}}

 

 

 

 

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