import java.util.concurrent.CountDownLatch;
时间: 2023-11-16 19:55:54 浏览: 41
import java.util.concurrent.CountDownLatch是Java并发包中的一个类,用于实现线程协作。它通过Sync内部类中的volatile int state属性来表示同步器的状态,并提供了await()和countDown()两个方法。其中,await()方法会使当前线程等待,直到CountDownLatch的计数器减为0,或者当前线程被中断。而countDown()方法则会将CountDownLatch的计数器减1。CountDownLatch可用于管理一组线程,适用于将一个任务分成若干线程执行,等到所有线程执行完,再进行汇总处理。
相关问题
将下列Java代码改为python代码:import java.util.ArrayList; import java.util.Comparator; import java.util.List; import java.util.concurrent.CountDownLatch; import java.net.*; public class Scanport { public static void main(String[] args) throws InterruptedException { String host = "120.46.209.149"; int startPort = 1; int endPort = 1024; int start = 0; int end = 0; int step = Math.round(endPort / 1000) + 1;// 四舍五入函数 for (int i = 1; i < step; i++) { start = startPort + (i - 1) * 1000; end = startPort + i * 1000; System.out.println("正在扫描" + start + "-" + end); scan(host, start, end); } } public static void scan(String host, int startPort, int endPort) throws InterruptedException { List<Integer> portList = new ArrayList<>(); final CountDownLatch latch = new CountDownLatch(endPort - startPort + 1); for (int port = startPort; port <= endPort; port++) { int finalPort = port; Thread thread = new Thread(new Runnable() { @Override public void run() { try { Socket socket = new Socket(); socket.connect(new InetSocketAddress(host, finalPort), 100); System.out.println("TCP端口" + finalPort + "开放"); portList.add(finalPort); } catch (Exception e) { } try { DatagramSocket dsocket = new DatagramSocket(finalPort); dsocket.close(); } catch (SocketException e) { portList.add(finalPort); System.out.println("UDP端口" + finalPort + "开放"); } latch.countDown(); } }); thread.start(); } latch.await(); portList.sort(new Comparator<Integer>() { @Override public int compare(Integer o1, Integer o2) { return o1.compareTo(o2); } }); } }
以下是将Java代码转换为Python代码后的结果:
```python
import socket
from concurrent.futures import ThreadPoolExecutor
import queue
import threading
def scan(host, startPort, endPort):
portList = []
q = queue.Queue()
for i in range(startPort, endPort+1):
q.put(i)
def worker():
while not q.empty():
port = q.get()
try:
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.settimeout(1)
s.connect((host, port))
print("TCP端口{}开放".format(port))
portList.append(port)
except:
pass
try:
s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
s.settimeout(1)
s.bind((host, port))
print("UDP端口{}开放".format(port))
portList.append(port)
except:
pass
threads = []
for i in range(50):
t = threading.Thread(target=worker)
threads.append(t)
t.start()
for t in threads:
t.join()
portList.sort()
return portList
def main():
host = "120.46.209.149"
startPort = 1
endPort = 1024
step = (endPort // 1000) + 1
for i in range(1, step):
start = startPort + (i - 1) * 1000
end = startPort + i * 1000
print("正在扫描{}-{}".format(start, end))
res = scan(host, start, end)
print(res)
if __name__ == "__main__":
main()
```
注意,在Python中没有类似于Java中的CountDownLatch类,因此我们使用了Python内置的queue和ThreadPoolExecutor来实现多线程扫描端口。此外,由于Python中的socket模块没有Java中的Socket类的connectTimeout属性,因此我们使用了settimeout方法来设置超时时间。
Android CountDownLatch .await的用法
Android中的CountDownLatch.await()方法用于使当前线程等待,直到计数器的值变为0。当调用await()方法时,如果计数器的值不为0,则当前线程将被挂起,直到计数器的值变为0或等待时间超时。该方法可以防止主线程在子线程还未完成任务时继续执行。
示例代码如下所示:
```
import java.util.concurrent.CountDownLatch;
public class CountDownLatchExample {
public static void main(String[] args) throws InterruptedException {
int threadCount = 5;
CountDownLatch countDownLatch = new CountDownLatch(threadCount);
for (int i = 0; i < threadCount; i++) {
new Thread(() -> {
// 子线程执行任务
System.out.println("子线程执行任务");
// 任务完成后调用countDown()方法
countDownLatch.countDown();
}).start();
}
// 主线程等待子线程完成任务
countDownLatch.await();
System.out.println("所有子线程任务执行完毕");
}
}
```