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【Java面试】如何实现非阻塞式生产者消费者?

1.问题描述

实现Java非阻塞式生产者消费者,用来解决,生产和消费对于资源访问不同步和造成资源冗余的问题

2.实现思想

  • 针对于同一资源,生产者生产前会前检测资源是否大于0,如果大于0,则生产者线程释放资源锁,进入waiting阶段,如果小于0,则生产者线程持有锁,并且生产资源,生产一定资源之后,通知消费者。
  • 消费者线程,去消费之前,会检测资源是否大于0,如果小于0,则阻塞等待,并且通知生产者生产资源,如果大于0,则消费资源,消费完成,唤醒生产者,生产资源。
  • 这样就实现了每次生产者生产都是生产一定的资源,等待消费者消费完成之后,才去继续生产

3.代码

3.1使用wait、notify

import java.util.ArrayList;
import java.util.List;
import java.util.Random;

public class Main {
	public static class Breads {
		private List<Integer> bordIntegers = new ArrayList<Integer>();
		public synchronized void add() {
			if (bordIntegers.size() > 0) {
				System.out.println("生产者检测到目前资源大于0,不生产");
				try {
					wait();
				} catch (InterruptedException e) {
					e.printStackTrace();
				}
			}

			System.out.println("生产者检测到目前资源小于0,开始生产");
			for (int i = 0; i < 5; i++) {
				bordIntegers.add(new Random().nextInt(1000));
			}

			try {
				Thread.sleep(1000);
			} catch (InterruptedException e) {
				e.printStackTrace();
			}
			notify();
		}

		public synchronized void del() {
			if (bordIntegers.size() <= 0) {
				System.out.println("消费者检测到目前资源小于0,通知生产者");
				try {
					wait();
				} catch (InterruptedException e) {
					e.printStackTrace();
				}
			}

			System.out.println("消费者检测到目前资源大于0,开始消费");
			for (int i = 0; i < bordIntegers.size(); i++) {
				System.out.println(bordIntegers.get(i));
			}
			bordIntegers.clear();
			try {
				Thread.sleep(1000);
			} catch (InterruptedException e) {
				e.printStackTrace();
			}
			notify();
		}
	}
	public static void main(String[] args) {
		Breads borad = new Breads();
		Thread createThread = new Thread(new Runnable() {

			@Override
			public void run() {
				while (true) {
					borad.add();
				}
			}
		});

		Thread consumethread = new Thread(new Runnable() {

			@Override
			public void run() {
				while (true) {
					borad.del();
				}
			}
		});

		createThread.start();
		consumethread.start();
		System.out.println("Main Thread exit!");
	}
}

3.2使用ArrayBlockingQueue

import java.util.concurrent.ArrayBlockingQueue;

public class Main {
	static ArrayBlockingQueue<Integer> bordBlockingQueue = new ArrayBlockingQueue<Integer>(
			10);
	public static void main(String[] args) {
		Thread createThread = new Thread(new Runnable() {

			@Override
			public void run() {
				while (true) {
					for (int i = 0; i < 10; i++) {
						try {
							bordBlockingQueue.put(i);
							System.out.println("生产者生产");
						} catch (InterruptedException e) {
							e.printStackTrace();
						}
					}
				}
			}
		});

		Thread consumethread = new Thread(new Runnable() {

			@Override
			public void run() {
				while (true) {
					while (!bordBlockingQueue.isEmpty()) {
						try {
							System.out.println("消费者消费");
							bordBlockingQueue.take();
						} catch (InterruptedException e) {
							// TODO Auto-generated catch block
							e.printStackTrace();
						}
					}
				}
			}
		});

		createThread.start();
		consumethread.start();
		System.out.println("Main Thread exit!");
	}
}
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