利用CountDownLatch和Semaphore测试案例
2024-10-21 12:37:32
package com.cxy; import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Semaphore; /**
* Created by Administrator on 2019/4/10.
*/
public class CxyDemo {
// 请求总数
public static int clientTotal = ; // 同时并发执行的线程数
public static int threadTotal = ; private static Map<Integer, Integer> map = new HashMap<>(); public static void main(String[] args) throws Exception {
ExecutorService executorService = Executors.newCachedThreadPool();
final Semaphore semaphore = new Semaphore(threadTotal);
final CountDownLatch countDownLatch = new CountDownLatch(clientTotal);
for (int i = ; i < clientTotal; i++) {
final int count = i;
executorService.execute(() -> {
try {
semaphore.acquire();
update(count);
semaphore.release();
} catch (Exception e) {
// log.error("exception" , e);
}
countDownLatch.countDown();
});
}
countDownLatch.await();
executorService.shutdown();
System.out.println(map.size());
//log.info("size:{}" , map.size());
} private static void update(int i) {
map.put(i, i);
} }
hashmap不是一个线程安全的类,上面就是对其进行测试
执行结果:
再执行一次:
可见不是线程安全的,
package com.cxy; import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.*; /**
* Created by Administrator on 2019/4/10.
*/
public class CxyDemo {
// 请求总数
public static int clientTotal = ; // 同时并发执行的线程数
public static int threadTotal = ; //private static Map<Integer, Integer> map = new HashMap<>();
private static ConcurrentHashMap<Integer, Integer> map = new ConcurrentHashMap<>(); public static void main(String[] args) throws Exception {
ExecutorService executorService = Executors.newCachedThreadPool();
final Semaphore semaphore = new Semaphore(threadTotal);
final CountDownLatch countDownLatch = new CountDownLatch(clientTotal);
for (int i = ; i < clientTotal; i++) {
final int count = i;
executorService.execute(() -> {
try {
semaphore.acquire();
update(count);
semaphore.release();
} catch (Exception e) {
// log.error("exception" , e);
}
countDownLatch.countDown();
});
}
countDownLatch.await();
executorService.shutdown();
System.out.println(map.size());
//log.info("size:{}" , map.size());
} private static void update(int i) {
map.put(i, i);
} }
测试concurrentHashmap,可以知道是线程安全的
package com.cxy; import java.util.HashMap;
import java.util.Hashtable;
import java.util.Map;
import java.util.concurrent.*; /**
* Created by Administrator on 2019/4/10.
*/
public class CxyDemo {
// 请求总数
public static int clientTotal = ; // 同时并发执行的线程数
public static int threadTotal = ; //private static Map<Integer, Integer> map = new HashMap<>();
// private static ConcurrentHashMap<Integer, Integer> map = new ConcurrentHashMap<>();
private static Map<Integer, Integer> map = new Hashtable<>(); public static void main(String[] args) throws Exception {
ExecutorService executorService = Executors.newCachedThreadPool();
final Semaphore semaphore = new Semaphore(threadTotal);
final CountDownLatch countDownLatch = new CountDownLatch(clientTotal);
for (int i = ; i < clientTotal; i++) {
final int count = i;
executorService.execute(() -> {
try {
semaphore.acquire();
update(count);
semaphore.release();
} catch (Exception e) {
// log.error("exception" , e);
}
countDownLatch.countDown();
});
}
countDownLatch.await();
executorService.shutdown();
System.out.println(map.size());
//log.info("size:{}" , map.size());
} private static void update(int i) {
map.put(i, i);
} }
hashtable也是线程安全:
总结:通过semaphore来模拟线程数,然后通过countdownlatch线程计数器来计算执行的线程,这样可以来模拟高并发测试
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