Java多线程高并发中解决ArrayList与HashSet和HashMap不安全的方案

package test.notsafe;
 
import java.util.*;
import java.util.concurrent.CopyOnWriteArrayList;
 
/**
 * 演示ArrayList的线程不安全问题及解决方案
 */
public class ThreadDemo2 {
    public static void main(String[] args) {
        //List<String> list = new ArrayList<>();
 
        //解决方法1：使用Vector
        //List<String> list = new Vector<>();
 
        //解决方法2：Collections
        //List<String> list = Collections.synchronizedList(new ArrayList<>());
 
        //解决方法3：CopyOnWriteArrayList
        List<String> list = new CopyOnWriteArrayList<>();
 
        for (int i = 0; i < 10; i++) {
            new Thread(() -> {
                list.add(UUID.randomUUID().toString().substring(0,8));
                System.out.println(list);
            },String.valueOf(i)).start();
        }
    }
}

    public boolean add(E e) {
        final ReentrantLock lock = this.lock;
        lock.lock();
        try {
            Object[] elements = getArray();
            int len = elements.length;
            Object[] newElements = Arrays.copyOf(elements, len + 1);
            newElements[len] = e;
            setArray(newElements);
            return true;
        } finally {
            lock.unlock();
        }
    }

package test.notsafe;
 
import java.util.Collections;
import java.util.HashSet;
import java.util.Set;
import java.util.UUID;
import java.util.concurrent.CopyOnWriteArraySet;
 
/**
 * 演示HashSet的线程不安全问题及解决方案
 */
public class ThreadDemo3 {
    public static void main(String[] args) {
        //Set<String> set = new HashSet<>();
 
        //解决方法1：Collections
        //Set<String> set = Collections.synchronizedSet(new HashSet<>());
 
        //解决方法2：CopyOnWriteArraySet
        Set<String> set = new CopyOnWriteArraySet<>();
 
        for (int i = 0; i < 20; i++) {
            new Thread(() -> {
                set.add(UUID.randomUUID().toString().substring(0,8));
                System.out.println(set);
            },String.valueOf(i)).start();
        }
    }
}

package test.notsafe;
 
import java.util.Collections;
import java.util.HashMap;
import java.util.Map;
import java.util.UUID;
import java.util.concurrent.ConcurrentHashMap;
 
/**
 * 演示HashMap的线程不安全问题及解决方案
 */
public class ThreadDemo4 {
    public static void main(String[] args) {
        //Map<String,Object> map = new HashMap<>();
 
        //解决方法1：Collections
        //Map<String,Object> map = Collections.synchronizedMap(new HashMap<>());
 
        //解决方法2：ConcurrentHashMap
        Map<String,Object> map = new ConcurrentHashMap<>();
 
        for (int i = 0; i < 10; i++) {
            String key = String.valueOf(i);
            new Thread(() -> {
                map.put(key,UUID.randomUUID().toString().substring(0,8));
                System.out.println(map);
            },String.valueOf(i)).start();
        }
    }
}