Day486&487&488

所有人出了门，保安才锁门

• CyclicBarrier循环栅栏

满足数量条件，就发车

人到齐了，就开会

• Semaphore信号量

“许可证”，数量有限

---

三、阻塞队列知道吗？

---

之前的学习笔记

• 为什么用？有什么好处？

• 知道哪些实现类吗？

• API

• 手写传统版生产者消费者模式

/******

@author 阿昌

@create 2021-05-22 20:58

---

• 用wait/notify来实现 生产者消费者模式

*/

public class ProducerConsumerModel {

//主函数

public static void main(String[] args) {

EventStorage eventStorage = new EventStorage();

Consumer1 consumer = new Consumer1(eventStorage);

Producer1 producer = new Producer1(eventStorage);

Thread threadConsumer = new Thread(consumer);

Thread threadProducer = new Thread(producer);

threadConsumer.start();

threadProducer.start();

}

}

//生产者

class Producer1 implements Runnable{

private EventStorage storage;

public Producer1(EventStorage storage) {

this.storage = storage;

}

@Override

public void run() {

for (int i = 0; i < 100; i++) {

storage.put();

}

}

}

//消费者

class Consumer1 implements Runnable{

private EventStorage storage;

public Consumer1(EventStorage storage) {

this.storage = storage;

}

@Override

public void run() {

for (int i = 0; i < 100; i++) {

storage.take();

}

}

}

//队列

class EventStorage{

private int maxSize;

private LinkedList storage;

public EventStorage(){

this.maxSize=10;

storage = new LinkedList<>();

}

//生成产品

public synchronized void put(){

//如果满了

while (storage.size()==maxSize){

try {

wait();

} catch (InterruptedException e) {

e.printStackTrace();

}

}

//如果没满

storage.add(new Date());

System.out.println(“生产者生产了产品，仓库里有了”+storage.size()+“个产品”);

notify();

}

//消费产品

public synchronized void take(){

//如果空了

while (storage.size()<=0){

try {

wait();

} catch (InterruptedException e) {

e.printStackTrace();

}

}

//如果没空

System.out.println(“消费者消费了产品，拿到了”+storage.poll()+“,现在仓库还剩下”+storage.size());

notify();

}

}

• 生产者消费者模式阻塞队列版

public class ConsumerProducer {

static class MySource{

private volatile boolean flag = true;

private BlockingQueue blockingQueue;

private AtomicInteger atomicInteger = new AtomicInteger();

public MySource(BlockingQueue queue)

{

this.blockingQueue = queue;

}

public void prod() throws InterruptedException {

String data = null;

while (flag){

data = atomicInteger.incrementAndGet()+“”;

if (blockingQueue.offer(data,2L, TimeUnit.SECONDS)){

System.out.println(“生产对象，并插入对类”);

}

Thread.sleep(1000);

}

this.flag = false;

System.out.println(“flag=false，停止生产…”);

}

public void consume() throws InterruptedException {

while (flag){

String data = blockingQueue.poll(2L, TimeUnit.SECONDS);

if (data != null || null != “”) {

System.out.println(“消费对象：”+data);

}else {

this.flag = false;

System.out.println(“消费者停止消费”);

}

Thread.sleep(1000);

}

}

public void clear(){

this.flag = false;

}

}

public static void main(String[] args) throws InterruptedException {

ArrayBlockingQueue queue = new ArrayBlockingQueue(10);

MySource mySource = new MySource(queue);

new Thread(new Runnable() {

@Override

public void run() {

try {

mySource.prod();

} catch (InterruptedException e) {

e.printStackTrace();

}

}

}).start();

new Thread(new Runnable() {

@Override

public void run() {

try {

mySource.consume();

} catch (InterruptedException e) {

e.printStackTrace();

}

}

}).start();

Thread.sleep(3000L);

System.out.println(“主线程停止操作”);

mySource.clear();

}

}

• Synchronized和Lock有什么区别？

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四、线程池用过吗？谈谈你的理解

---

https://achang.blog.youkuaiyun.com/article/details/117606362

• 为什么需要使用线程池

• 反复创建线程开销大

• 过多的线程会导致内存消耗

• 线程池的好处

• 加快响应速度

• 便于线程的管理控制，方便数据统计

• 合理利用CPU和内存

• 线程池构造函数的参数

• 流程图

• 是否需要增加线程的判断

• corePoolSzie

• workQueue

• maxPoolSize

• 说说线程池底层原理----也就是线程池创建7大参数

• 线程池的拒绝策略，请你谈谈

• 为什么工作中尽量不使用Executors去创建线程池？

• 线程池合理配置数

• CPU密集型

• CPU核数*2

• IO型

• CPU核数/ 1 * 0.9