ArrayList线程不安全三种解决情况

在多线程高并发的情况下arrayList会抛出concurrentModificationException

解决情况

1.vector
2. Collections.synchronizedList(new ArrayList<>());
3. 用JUC包下的CopyOnWriteArrayList
源码分析

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();
        }
    }