copyonwriteArrayList的lock锁

Posted 2020-11-12 otways

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();
        }

其中的　　volatile关键字：
保证系统内存一致性

举个例子：多个cpu，cpu1执行了update+1操作，cpu2做修改时会拉取内存要修改的数，保证update+1时内存成功修改