多线程  并发  同步  性能分析

/*** 线程安全: 在并发时保证数据的正确性、效率尽可能高* synchronized* 1、同步方法* 2、同步块* @author Administrator**/ public class SynBlockTest03 {public static void main(String[] args) {//一份资源SynWeb12306 web =new SynWeb12306();//多个代理new Thread(web,"码畜").start();new Thread(web,"码农").start();new Thread(web,"码蟥").start();;}}class SynWeb12306 implements Runnable{//票数private int ticketNums =10;private boolean flag = true;@Overridepublic void run() {while(flag) {try {Thread.sleep(100);} catch (InterruptedException e) {e.printStackTrace();}test5();}} //线程安全:尽可能锁定合理的范围(不是指代码 指数据的完整性)//double checkingpublic void test5() {if(ticketNums<=0) {//考虑的是没有票的情况flag = false;return ;}synchronized(this) { if(ticketNums<=0) {//考虑最后的1张票flag = false;return ;}//模拟延时try {Thread.sleep(200);} catch (InterruptedException e) {e.printStackTrace();}System.out.println(Thread.currentThread().getName()+"-->"+ticketNums--);}}//线程不安全 范围太小锁不住public void test4() {synchronized(this) {if(ticketNums<=0) {flag = false;return ;}}//模拟延时try {Thread.sleep(200);} catch (InterruptedException e) {e.printStackTrace();}System.out.println(Thread.currentThread().getName()+"-->"+ticketNums--);}//线程不安全 ticketNums对象在变 锁的应该是地址，锁的应该是不变的东西public void test3() {synchronized((Integer)ticketNums) {if(ticketNums<=0) {flag = false;return ;}//模拟延时try {Thread.sleep(200);} catch (InterruptedException e) {e.printStackTrace();}System.out.println(Thread.currentThread().getName()+"-->"+ticketNums--);}}//线程安全 范围太大 -->效率低下public void test2() {//用this没有问题，因为把对象给锁定啦！ 要锁ticketNums和flag 这两个变量，只有这两个锁住啦，才是真的锁住啦synchronized(this) {if(ticketNums<=0) {flag = false;return ;}//模拟延时try {Thread.sleep(200);} catch (InterruptedException e) {e.printStackTrace();}System.out.println(Thread.currentThread().getName()+"-->"+ticketNums--);}}//线程安全 同步public synchronized void test1() {if(ticketNums<=0) {flag = false;return ;}//模拟延时try {Thread.sleep(200);} catch (InterruptedException e) {e.printStackTrace();}System.out.println(Thread.currentThread().getName()+"-->"+ticketNums--);} }

 

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快乐影院  订票操作

/*** 快乐影院* @author Administrator**/ public class HappyCinema {public static void main(String[] args) {Cinema c=new Cinema(1,"happy dym");new Thread(new Customer(c, 2),"止兮").start();new Thread(new Customer(c, 1),"苍凌").start();} } //顾客 class Customer implements Runnable{Cinema cinema;int seats;public Customer(Cinema cinema, int seats) {super();this.cinema = cinema;this.seats = seats;}@Overridepublic void run() {synchronized(cinema) {boolean flag=cinema.bookTickets(seats);if(flag) {System.out.println("出票成功"+Thread.currentThread().getName()+"->票数为："+seats);}else {System.out.println("出票失败"+Thread.currentThread().getName()+"->位置不够");}}}}//影院 class Cinema{int available; //可用的位置个数String name; //名称public Cinema(int available, String name) {super();this.available = available;this.name = name;}//购票public boolean bookTickets(int seats) {System.out.println("可用的位置个数为："+available);if(seats>available) {return false;}available -= seats;return true;} }

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快乐影院  订票操作  改良版

import java.util.ArrayList; import java.util.List;/*** 快乐影院* @author Administrator**/ public class HappyCinema2 {public static void main(String[] args) {//可用位置List<Integer> available=new ArrayList<Integer>();available.add(1);available.add(3);available.add(4);available.add(5);available.add(6);available.add(9);//顾客需要的位置List<Integer> seat1=new ArrayList<Integer>();seat1.add(1);seat1.add(2);List<Integer> seat2=new ArrayList<Integer>();seat2.add(3);seat2.add(5);seat2.add(9);DymCinema d=new DymCinema(available, "happy dym");new Thread(new HappyCustomer(d, seat1),"止兮").start();new Thread(new HappyCustomer(d, seat2),"苍凌").start();} } //顾客 class HappyCustomer implements Runnable{DymCinema cinema;List<Integer> seats;public HappyCustomer(DymCinema cinema, List<Integer> seats) {this.cinema = cinema;this.seats = seats;}@Overridepublic void run() {synchronized(cinema) {boolean flag=cinema.bookTickets(seats);if(flag) {System.out.println("出票成功"+Thread.currentThread().getName()+"-<位置为:"+seats);}else {System.out.println("出票失败"+Thread.currentThread().getName()+"-<位置不够"); }}}}//影院 class DymCinema{List<Integer> available; //可用的位置String name; //名称public DymCinema(List<Integer> available, String name) {this.available = available;this.name = name;}//购票public boolean bookTickets(List<Integer> seats) {System.out.println("欢迎光临"+this.name+",当前的可用位置为："+available);List<Integer> copy=new ArrayList<Integer>();copy.addAll(available);//相减copy.removeAll(seats);//判断大小if(available.size()-copy.size()!=seats.size()) {return false;}//订票成功available=copy;return true; } }

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快乐火车票

/*** 快乐火车票* @author Administrator**/ public class Happy12306 {public static void main(String[] args) {Web12306 c=new Web12306(4,"happy dym");new Passenger(c,"止兮",2).start();new Passenger(c,"苍凌",1).start();} } //顾客 class Passenger extends Thread{int seats;public Passenger(Runnable target,String name,int seats) {super(target,name);this.seats=seats;} } // 火车票网 class Web12306 implements Runnable{int available;//可用的位置String name; //名称public Web12306(int available, String name) {this.available = available;this.name = name;}@Overridepublic void run() {Passenger p=(Passenger)Thread.currentThread();boolean flag=this.bookTickests(p.seats);if(flag) {System.out.println("出票成功"+Thread.currentThread().getName()+"->订位置的个数："+p.seats);}else {System.out.println("出票失败"+Thread.currentThread().getName()+"->位置不够");}}//购票public synchronized boolean bookTickests(int seats) {System.out.println("可用位置个数为"+available);if(seats>available) {return false;}available -= seats;return true;}}

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操作并发容器

import java.util.concurrent.CopyOnWriteArrayList; /*** 线程安全：操作并发容器* @author Administrator**/ public class SynContainer {public static void main(String[] args) throws InterruptedException {CopyOnWriteArrayList<String> list=new CopyOnWriteArrayList<String> ();for(int i=0;i<10000;i++) {new Thread(()->{list.add(Thread.currentThread().getName());}) .start();}Thread.sleep(1000);System.out.println(list.size());} }

总结

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