不定数量多线程轮询打印i++-优快云博客

本文介绍了一个使用Java实现的细粒度并发控制案例，通过ReentrantLock和Condition实现了多个线程间的精确同步，确保了线程按特定顺序执行并打印计数器值，展示了高并发场景下线程调度的细节。

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package dmeo;

import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;

public class LockTest {
    private static Lock lock = new ReentrantLock();
    static List<Condition> conditions;
    private static int count = 0;
    private static int lockNumber1=0;
    
    static void init(int lockNumber) throws InterruptedException {
    	lockNumber1=lockNumber;
    	conditions=new ArrayList<>(lockNumber);
    	Condition condition;
        //细粒度的condition
    	for(int i=0;i<lockNumber;i++) {
    		condition=lock.newCondition();
    		conditions.add(condition);
    	}
        //启动所有线程
    	for(int i=0;i<lockNumber;i++) {
    		new ThreadA(i).start();
    	}
    }
    
    
    static class ThreadA extends Thread {
        //把自己在condition中的位置记住
    	private int i;
    	
    	public ThreadA(int i) {
    		this.i=i;
		}
        @Override
        public void run() {
            try {
                lock.lock();
                while(count<99) {
                    while (count % lockNumber1 != i){
                        conditions.get(i).await();; //锁住自己
                    }
                    if(count > 100 ) break;
                    System.out.println(Thread.currentThread().getId()+":"+count++);
                    //如果是最后一个线程,就唤醒第一个.
                    //直接唤醒下一个线程
                    if(i != lockNumber1-1) {
                    	conditions.get(i+1).signal();
                    }
                    else {
                    	conditions.get(0).signal();
                    }
                }

            } catch (InterruptedException e) {
                e.printStackTrace();
            } finally {
                lock.unlock();
            }
        }
    }

    public static void main(String[] args) throws InterruptedException {
    	init(3);
    }
    
}