Java线程安全同步容器
2024-09-06 07:21:13
线程安全同步容器(使用 synchronized关键字)
1.ArrayList->Vector,Stack
2.HashMap->HashTable(key、value不能为null)
3.Collections.synchronizedXXX(List、Set、Map)
同步容器也有线程不安全的情况 stack继承vector
package com.alan.concurrency.example.syncContainer; import com.alan.concurrency.annoations.NotThreadSafe;
import com.alan.concurrency.annoations.ThreadSafe;
import lombok.extern.slf4j.Slf4j; import java.util.Vector;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Semaphore; @Slf4j
@NotThreadSafe
public class VectorExample2 { private static Vector<Integer> vector = new Vector<>(); public static void main(String[] args) { while (true){ for (int i = 0; i < 10; i++) {
vector.add(i);
} Thread thread1 = new Thread(){
public void run(){
for (int i = 0; i < vector.size(); i++) {
vector.remove(i);
}
}
}; Thread thread2 = new Thread(){
public void run(){
for (int i = 0; i <vector.size(); i++) {
vector.get(i);
}
}
}; thread1.start();
thread2.start();
} }
}
HashTable同步容器
package com.alan.concurrency.example.syncContainer; import com.alan.concurrency.annoations.NotThreadSafe;
import lombok.extern.slf4j.Slf4j; import java.util.HashMap;
import java.util.Hashtable;
import java.util.Map;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Semaphore; @Slf4j
public class HashTableExample { // 请求总数
public static int clientTotal = 5000; // 同时并发执行的线程数
public static int threadTotal = 200; 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 = 0; 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();
log.info("size:{}", map.size());
} private static void update(int i) {
map.put(i, i);
}
}
Collections.synchronized相关同步容器
1、public static List<Integer> list = Collections.synchronizedList(new ArrayList<>()) ;
2、 public static Set<Integer> set = Collections.synchronizedSet(new HashSet<>()) ;
3、 private static Map<Integer, Integer> map = Collections.synchronizedMap(new HashMap<>()) ;
2、 public static Set<Integer> set = Collections.synchronizedSet(new HashSet<>()) ;
3、 private static Map<Integer, Integer> map = Collections.synchronizedMap(new HashMap<>()) ;
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