Queue introductory small case
This article does not talk about any technology, just write a few introductory small cases related to threads and queues, those who are interested can take a look, and those who are not interested can stop here.
public class QueueDemo {
public static void main(String[] args) {
// 创建一个双端队列
ArrayDeque<Object> deque = new ArrayDeque<>();
//添加元素
deque.offer("春花");
deque.offer("夏夜");
deque.offer("秋香");
deque.offer("冬梅");
//移出元素
// System.out.println(deque.poll());
// 从头部加元素
deque.addFirst("石榴");
// System.out.println(deque);
// 从尾部加元素
deque.addLast("武状元");
// System.out.println(deque);
for(int i=1;i<100;i++){
deque.offer("华安"+i);
}
//多线程测试,安全问题
for(int i=0;i<4;i++){
new ConsumeQueue(deque).start();;
}
}
}
//自定义线程
public class ConsumeQueue extends Thread{
private ArrayDeque<Object> deque;
public ConsumeQueue(ArrayDeque<Object> deque) {
this.deque = deque;
}
@Override
public void run() {
while(true){
System.out.println(Thread.currentThread().getId()+"......."+deque.poll());
try {
sleep(1000);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
}
The result of running multiple threads:
Speaking of threads, by the way, there are three ways to implement threads. The first is to inherit the Thread class used above, and the second is to implement the Runnable interface (see the previous article <<A brief understanding of multithreading>>) , the third is the Callable interface under java.util.concurrent.
Callable entry small case
public class CallableDemo {
public static void main(String[] args) throws Exception {
//1.实现Callable
Callable<String> callable=new Callable<String>() {
@Override
public String call() throws Exception {
// TODO Auto-generated method stub
return "小淫虫周伯通";
}
};
//2.创建futureTask
FutureTask<String> futureTask = new FutureTask<String>(callable);
//3.执行
new Thread(futureTask).start();
try {
Thread.sleep(5000);
System.out.println(futureTask.get());
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}When looking for related apis, I found that under java.util.concurrent, there is a queue called BlockingQueue, which is a blocking queue:
- When the queue is full, enter the queue operation
- Dequeue operation when the queue is empty
BlockingQueue small case:
public class BlockQueueDemo {
public static void main(String[] args) throws Exception {
final BlockingQueue<Object> blockingQueue = new ArrayBlockingQueue<>(100);
/*for(int i=0;i<11;i++){
//加多了会阻塞(队列容量为10)
blockingQueue.put("韦小宝"+i);
}
for(int i=0;i<20;i++){
//取多了也会阻塞(队列中只有10个值)
System.out.println(blockingQueue.take());
}*/
//多线程测试
//一个线程生产
new Thread(){
public void run() {
for(int i=1;i<100;i++){
try {
blockingQueue.put("韦小宝"+i);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
};
}.start();
//两个线程在消费
new Thread(){
public void run() {
while(true){
try {
System.out.println(Thread.currentThread().getId()+"...."+blockingQueue.take());
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
};
}.start();
new Thread(){
public void run() {
while(true){
try {
System.out.println(Thread.currentThread().getId()+"...."+blockingQueue.take());
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
};
}.start();
}
}Blocking when the added element is larger than the queue capacity, and also blocking after removing all the elements with the best speed in
the queue
Now that we talk about threads, let's talk about the thread pool.
Thread pool entry small case:
//线程池
public class ThreadPoolDemo {
//固定线程池,底层是无界队列
@Test
public void testFixedThreadPool(){
//创建6个线程
ExecutorService threadPool = Executors.newFixedThreadPool(6);
for(int i=0;i<6;i++){
threadPool.submit(new Runnable() {
@Override
public void run() {
// TODO Auto-generated method stub
System.out.println(Thread.currentThread().getId()+"风华绝代石榴姐");
}
});
}
}
//单一线程,在执行任务时,会依次执行,底层是无界队列
@Test
public void testSingleThreadExecutor(){
//创建6个线程
ExecutorService threadPool = Executors.newSingleThreadExecutor();
for(int i=0;i<6;i++){
threadPool.submit(new Runnable() {
@Override
public void run() {
// TODO Auto-generated method stub
System.out.println(Thread.currentThread().getId()+"武功盖世武状元");
System.out.println(System.currentTimeMillis());
}
});
}
}
//创建非固定数量,可缓存的线程池,当提交的任务起起伏伏时,会自动创建或减少执行线程数量
@Test
public void testCachedThread(){
//创建6个线程
ExecutorService threadPool = Executors.newCachedThreadPool();
for(int i=0;i<50;i++){
threadPool.submit(new Runnable() {
@Override
public void run() {
// TODO Auto-generated method stub
System.out.println(Thread.currentThread().getId()+"绝命书生一点红");
System.out.println(System.currentTimeMillis());
}
});
}
try {
Thread.sleep(5000);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
System.out.println("--------------------------------------------------");
for(int i=0;i<10;i++){
threadPool.submit(new Runnable() {
@Override
public void run() {
// TODO Auto-generated method stub
System.out.println(Thread.currentThread().getId()+"遛鸟狂魔发飙王");
System.out.println(System.currentTimeMillis());
}
});
}
}
//后面还有定时执行线程池等,有想要了解的可以去练下,我不多写了.....
}