Java线程安全同步容器

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<>()) ;