經典面試題: 手寫生産者 /消費者模型

通常情況下，有5種方式來實作

1. synchronized + wait() + notify() 方式
2. 可重入鎖ReentrantLock （配合Condition）
3. BlockingQueue 阻塞隊列方式
4. 信号量Semaphore 方式
5. 管道輸入輸出流PipedInputStream和PipedOutputStream 方式

下面代碼是 采用 第二種方式

package interview.producer_consumer;

import lombok.SneakyThrows;

import java.util.LinkedList;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.ReentrantLock;

public class Test {

    public static void main(String[] args) {

        MyDeque myDeque = new MyDeque(10);
        Producer_ producer_ = new Producer_(myDeque);
        Consumer_ consumer_ = new Consumer_(myDeque);
        Producer_ producer_2 = new Producer_(myDeque);
        Consumer_ consumer_2 = new Consumer_(myDeque);

        new Thread( producer_).start();
        new Thread( consumer_).start();

        new Thread( producer_2).start();
        new Thread( consumer_2).start();
    }
}

class MyDeque {
    int max_size;
    LinkedList<Integer> linkedList = new LinkedList<Integer>();
    ReentrantLock reentrantLock = new ReentrantLock();
    Condition producer_condition = reentrantLock.newCondition();//生産者條件:消息隊列滿了阻塞
    Condition consumer_condition = reentrantLock.newCondition();//消費者條件:消息隊列為空阻塞

    volatile int data = 1;



    public MyDeque(int max_size){
        this.max_size = max_size;
    }
    public void  put(){
        reentrantLock.lock();
        try {
            if (linkedList.size() >= this.max_size){
                System.out.println(" 隊列已滿" + Thread.currentThread().getName() + "無法添加資料");
                producer_condition.await();
            }
            System.out.print( Thread.currentThread().getName() +"生産者添加資料" + data + "\t");
            linkedList.add( this.data);
            data++;

            System.out.println("隊列資料" + linkedList);
            consumer_condition.signalAll();
        }catch (Exception e){
            e.printStackTrace();
        }finally {
            reentrantLock.unlock();
        }
    }
    public void take(){
        reentrantLock.lock();
        try {
            if (linkedList.size() >0 ){
                Integer integer = linkedList.removeFirst();
                System.out.println(Thread.currentThread().getName() +  "消費者 消費資料" + integer);
            }else {
                System.out.println("隊列中無資料, 消費者等待");
                producer_condition.signalAll();
                consumer_condition.await();
            }


        }catch (Exception e){
            e.printStackTrace();
        }finally {
            reentrantLock.unlock();
        }
    }
}

class Producer_ implements Runnable{
    MyDeque myDeque;
    public Producer_(MyDeque myDeque ){
        this.myDeque = myDeque;
    }

    @SneakyThrows
    @Override
    public void run() {
        while (true){
            myDeque.put();
            Thread.sleep(1000);
        }
    }
}

class Consumer_ implements Runnable{
    MyDeque myDeque;
    public   Consumer_(MyDeque myDeque ){
        this.myDeque = myDeque;
    }

    @SneakyThrows
    @Override
    public void run() {
       while (true){
           myDeque.take();
           Thread.sleep(1500);
       }

    }
}