模拟高并发

墨蓝 2022-03-28 05:22 172阅读 0赞

这几天想鼓捣一下高并发，之前对并发数据一致性处理，使用的synchronized关键字，想试试lock，只不过效果不理想啊，

阶段一：用的lock.lock()和unLock()方法配合，只是保证了数据一致性，只不过会导致有的线程取不到结果

阶段二：使用lock.tryLock()和unLock()方法配合，当试图加锁失败的时候，再次调用业务方法，数据一致性和线程执行成功都得到了保证，但是执行时间有点长，和synchronized没法比啊(继续学习吧。。。)

使用synchronized关键字

import java.util.ArrayList;
    import java.util.List;
    import java.util.concurrent.Callable;
    import java.util.concurrent.CountDownLatch;
    import java.util.concurrent.ExecutorService;
    import java.util.concurrent.Executors;
    import java.util.concurrent.FutureTask;
    import java.util.concurrent.locks.Lock;
    import java.util.concurrent.locks.ReadWriteLock;
    import java.util.concurrent.locks.ReentrantLock;
    import java.util.concurrent.locks.ReentrantReadWriteLock;
    
    /**
     * 高并发模拟
     * */
    public class HighConcurrenceBuy {
    	private ReadWriteLock mReadWriteLock = new ReentrantReadWriteLock();
    //	private Lock lock = mReadWriteLock.readLock();
    	private Lock lock = new ReentrantLock();
    	private People people;
    	private Train train;
    
    	public Train getTrain() {
    		return train;
    	}
    
    	public void setTrain(Train train) {
    		this.train = train;
    	}
    	
    	public void buyTicket(People people) {//卖票
    		synchronized (train) {
    			int ticket = train.getTicket();
    			people.setTicketNumber(ticket);
    			ticket--;
    			train.setTicket(ticket);
    		}
    
    //		if (lock.tryLock()) {
    //			try {
    //				int ticket = train.getTicket();
    //				people.setTicketNumber(ticket);
    //				ticket--;
    //				train.setTicket(ticket);
    //			} catch (Exception e) {
    //				// TODO Auto-generated catch block
    //				e.printStackTrace();
    //			} finally {
    //				lock.unlock();
    //			}
    //		}else {
    //			try {
    //				Thread.currentThread().sleep(100);
    //				buyTicket(people);
    //			} catch (InterruptedException e) {
    //				// TODO Auto-generated catch block
    //				e.printStackTrace();
    //			}
    //		}
    	}
    	
    	public void refundable(People people) {//退票
    		int ticket = train.getTicket();
    		ticket++;
    		train.setTicket(ticket);
    	}
    
    	public People getPeople() {
    		return people;
    	}
    
    	public void setPeople(People people) {
    		this.people = people;
    	}
    	
    	private static int threadSize = 10000;
    	private static CountDownLatch countDown = new CountDownLatch(threadSize);
    	public static void main(String [] args) {
    
    		Train train = new Train("东风",100000);
    		HighConcurrenceBuy buy = new HighConcurrenceBuy();
    		buy.setTrain(train);
    		
    		long startTime = System.currentTimeMillis();
    		System.out.println("主线程start use:" + startTime);
    
    		
    		ExecutorService executor = Executors.newFixedThreadPool(2000);
    		for(int i = 0;i<threadSize;i++) {
    			
    			People people = new People("王"+i);
    			
    			Callable<String> call1 = new Callable<String>() {
    			    @Override  
    			    public String call() throws Exception {  
    			        Thread.sleep(100);
    			        countDown.countDown(); 
    					buy.buyTicket(people);
    
    					System.out.println(Thread.currentThread().getName()+" user time "+(System.currentTimeMillis()-startTime));
    			        //return the thread name executing this callable task  
    			        return Thread.currentThread().getName();  
    			    } 
    				
    			};
    			FutureTask<String> future1 = new FutureTask<String>(call1);
    			executor.execute(future1);
    			
    		}
    		
    		try {
    			countDown.await();
    			System.out.println("end use:" + (System.currentTimeMillis()-startTime));
    		} catch (InterruptedException e) {
    			// TODO Auto-generated catch block
    			e.printStackTrace();
    		}
    		
    	}
    }

执行结果：

...
    pool-1-thread-649 user time 1025
    王9989买到了票编号：90001
    东风号列车还剩：90000张票
    pool-1-thread-1904 user time 1025

使用lock

执行结果：

...
    东风号列车还剩：90001张票
    pool-1-thread-691 user time 3361
    东风号列车还剩：90000张票
    王9629买到了票编号：90001
    pool-1-thread-451 user time 3440

这让我情何以堪，继续学习吧，是不是哪里写的不对啊，望程序员的小哥哥小姐姐临幸