[英]Java how to avoid using Thread.sleep() in a loop
從我的主要開始,我開始了兩個名為生產者和消費者的線程。 兩者都包含while(true)
循環。 生產者循環是 UDP 服務器,因此它不需要睡眠。 我的問題出在消費者循環中。 消費者循環從鏈接隊列中刪除對象並將其傳遞給函數以進行進一步處理。 根據研究,在循環中使用線程睡眠不是一個好習慣,因為有時 O/S 不會在設置時間結束時釋放。 如果我在應用程序理想時刪除線程睡眠,它會將 CPU 拖到 20% 到 30%。
class Producer implements Runnable {
private DatagramSocket dsocket;
FError fer = new FError();
int port =1548;
ConcurrentLinkedQueue<String> queue;
Producer(ConcurrentLinkedQueue<String> queue){
this.queue = queue;
}
@Override
public void run() {
try {
// Create a socket to listen on the port.
dsocket = new DatagramSocket(port);
// Create a buffer to read datagrams into.
byte[] buffer = new byte[30000];
// Create a packet to receive data into the buffer
DatagramPacket packet = new DatagramPacket(buffer,
buffer.length);
while (true) {
try {
// Wait to receive a datagram
dsocket.receive(packet);
//Convert the contents to a string,
String msg = new String(buffer, 0, packet.getLength());
int ltr = msg.length();
// System.out.println("MSG =" + msg);
if(ltr>4)
{
SimpleDateFormat sdfDate = new SimpleDateFormat ("yyyy-MM-dd HH:mm:ss");//dd/MM/yyyy
Date now = new Date();
String strDate = sdfDate.format(now);
//System.out.println(strDate);
queue.add(msg + "&" + strDate);
// System.out.println("MSG =" + msg);
}
// Reset the length of the packet before reusing it.
packet.setLength(buffer.length);
} catch (IOException e) {
fer.felog("svr class", "producer", "producer thread",e.getClass().getName() + ": " + e.getMessage());
dsocket.close();
break;
}
}
} catch (SocketException e) {
fer.felog("svr class", "producer","Another App using the udp port " + port, e.getClass().getName() + ": " + e.getMessage());
}
}
}
class Consumer implements Runnable {
String str;
ConcurrentLinkedQueue<String> queue;
Consumer(ConcurrentLinkedQueue<String> queue) {
this.queue = queue;
}
@Override
public void run() {
while (true) {
try {
while ((str = queue.poll()) != null) {
call(str); // do further processing
}
} catch (IOException e) {
ferpt.felog("svr class", "consumer", "consumer thread", e.getClass().getName() + ": " + e.getMessage());
break;
}
try {
Thread.sleep(500);
} catch (InterruptedException ex) {
ferpt.felog("svr class", "consumer","sleep", ex.getClass().getName() + ": " + ex.getMessage());
}
}
}
}
您可以更改代碼以合並ScheduledExecutorService
,而不是讓 Consumer extend Runnable
,該服務每半秒運行一次隊列輪詢,而不是讓線程休眠。 這方面的一個例子是
public void schedule() {
ScheduledExecutorService executor = Executors.newSingleThreadScheduledExecutor();
executor.scheduleAtFixedRate(() -> {
String str;
try {
while ((str = queue.poll()) != null) {
call(str); // do further processing
}
} catch (IOException e) {
ferpt.felog("svr class", "consumer", "consumer thread", e.getClass().getName() + ": " + e.getMessage());
}
}, 0, 500, TimeUnit.MILLISECONDS);
}
解決問題的正確方法是使用阻塞隊列。 它為您提供了幾個優勢:
這是一個小演示,您可以使用它:
import java.util.concurrent.ArrayBlockingQueue;
import java.util.concurrent.BlockingQueue;
public class ProdConsTest {
public static void main(String[] args) throws InterruptedException {
final BlockingQueue<Integer> queue = new ArrayBlockingQueue<>(10);
final Runnable producer = () -> {
for (int i = 0; i < 1000; i++) {
try {
System.out.println("Producing: " + i);
queue.put(i);
//Adjust production speed by modifying the sleep time
Thread.sleep(100);
} catch (InterruptedException e) {
//someone signaled us to terminate
break;
}
}
};
final Runnable consumer = () -> {
while (true) {
final Integer integer;
try {
//Uncomment to simulate slow consumer:
//Thread.sleep(1000);
integer = queue.take();
} catch (InterruptedException e) {
//someone signaled us to terminate
break;
}
System.out.println("Consumed: " + integer);
}
};
final Thread consumerThread = new Thread(consumer);
consumerThread.start();
final Thread producerThread = new Thread(producer);
producerThread.start();
producerThread.join();
consumerThread.interrupt();
consumerThread.join();
}
}
現在取消消費者中的sleep()
注釋並觀察應用程序發生了什么。 如果您正在使用基於計時器的解決方案,例如建議的ScheduledExecutorService
或者您正忙於等待,那么使用快速生產者,隊列將無法控制地增長並最終使您的應用程序崩潰
讓消費者wait()
在一個都可以訪問的對象上,讓生產者notify()
在有新消息時監聽這個對象。 消費者應該刪除所有消息,而不是像示例中那樣只刪除一條消息。
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