模擬搶購火車票

package com.cl.syn;

//不安全買票，會出現多人買同一張票，導致票數出現負數
//解決，synchronized，同步方法，讓多個執行緒之間做到排隊等待
//缺點：若將一個大的方法申明synchronized將會影響效率

public class UnsafeBuyTicket {

    public static void main(String[] args) {
        BuyTicket station = new BuyTicket();

        new Thread(station,"帥氣的我").start();
        
 
new Thread(station,"老黃牛").start();
        new Thread(station,"小黃").start();
    }
}

class BuyTicket implements Runnable{

    //票
    private int ticketNums=10;
    boolean flag=true;//外部停止方式
    @Override
    public void run() {
        //買票
        while (flag){
            buy();
        }
    }

    
 
private synchronized void buy(){
        //判斷是否有票
        if (ticketNums<=0){
            flag=false;
            return;
        }
        //模擬延時,放大存在問題
        try {
            Thread.sleep(100);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        //那個程序搶到票
        System.out.println(Thread.currentThread().getName()+"拿到"+ticketNums--);
    }
}
 

模擬多人在統一賬戶取錢

package com.cl.syn;

//不安全的取錢
//模擬兩個人去銀行取錢，賬戶
//解決：
//synchronized默認同步的是this，本身
//因此要用同步塊，

public class UnsafeBank {
    public static void main(String[] args) {
        //賬戶
        Account account = new Account(1000, "結婚基金");

        Drawing you=new Drawing(account,50,"你");
        Drawing friend=new Drawing(account,100,"friend");

        you.start();
        friend.start();
    }
}


//賬戶
class Account{
    int money;//餘額
    String name;//卡名

    public Account(int money,String name){
        this.money=money;
        this.name=name;
    }
}


//銀行
class Drawing extends Thread{
    Account account;//賬戶
    int drawingMoney;//取了多少錢
    int nowMoney;//手裡有多少錢

    public Drawing(Account account,int drawingMoney,String name){
        super(name);
        this.account=account;
        this.drawingMoney=drawingMoney;

    }

    //取錢

    @Override
    public void run() {

        //鎖的物件就是變化的量，需要增刪改查的物件
        synchronized (account){
            //判斷有沒有錢
            if(account.money-drawingMoney<0){
                System.out.println(Thread.currentThread().getName()+"錢不夠，取不了");
                return;
            }

            try {
                Thread.sleep(100);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }

            //卡內餘額
            account.money-=drawingMoney;
            //手裡的錢
            nowMoney+=drawingMoney;

            System.out.println(account.name+"餘額："+account.money);
            System.out.println(this.getName()+"手裡的錢："+nowMoney);
        }
    }

}

測試JUC安全型別的集合

package com.cl.syn;

//util.concurrent，併發包
import java.util.concurrent.CopyOnWriteArrayList;

//測試JUC安全型別的集合
public class TestJUC {
    public static void main(String[] args) {
        CopyOnWriteArrayList<String> list=new CopyOnWriteArrayList<String>();
        for (int i = 0; i < 10000; i++) {
            new Thread(()->{
                list.add(Thread.currentThread().getName());
            }).start();
        }

        try {
            Thread.sleep(3000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        System.out.println(list.size());
    }
}

瞭解lock鎖

package com.cl.syn;

import java.util.concurrent.locks.ReentrantLock;

//測試lock鎖,加鎖：lock.lock()
//          解鎖：lock.unlock();
public class TestLock {
    public static void main(String[] args) {
        TestLock2 testLock2 = new TestLock2();

        new Thread(testLock2).start();
        new Thread(testLock2).start();
        new Thread(testLock2).start();
    }

}

class TestLock2 implements Runnable{

    int ticketNums=10;

    //定義lock鎖
    private final ReentrantLock lock=new ReentrantLock();

    @Override
    public void run() {
        while (true){

            try {
                lock.lock();//加鎖
                if (ticketNums>0){
                    try {
                        Thread.sleep(1000);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                    System.out.println(ticketNums--);
                }else {
                    break;
                }
            }finally {
                //解鎖
                lock.unlock();
            }

        }
    }
}