简介

相对于synchronized关键字，ReentrantLock具备以下特点：

前言

​ 陈皓叔叔的这个专栏之前就有所耳闻并大致过了一遍，如今重新精读本专栏，认真学习，对整体的学习方向进行把握，并且进行总结。

简介

秒杀从规模上可以分为以下两类：

简介

Basic thread blocking primitives for creating locks and other synchronization classes. – Java Doc

简介

通常情况下，在Java中，++i这类自增/自减运算符在并发环境中不能保证并发安全。需要通过加锁才能解决并发环境下的原子性问题。Atomic原子类通过CAS方式来解决线程安全问题，CAS是一种无锁算法（乐观锁），乐观锁多用于“读多写少“的环境，避免频繁加锁影响性能；而悲观锁多用于”写多读少“的环境，避免频繁失败和重试影响性能。

定义

The Java programming language allows threads to access shared variables (§17.1).As a rule, to ensure that shared variables are consistently and reliably updated, a thread should ensure that it has exclusive use of such variables by obtaining a lock that, conventionally, enforces mutual exclusion for those shared variables.The Java programming language provides a second mechanism, volatile fields,that is more convenient than locking for some purposes.A field may be declared volatile, in which case the Java Memory Model ensures that all threads see a consistent value for the variable (§17.4).