【Java并发】原子类源码分析之AtomicLong

2024-08-30 10:32
文章标签 java 分析 源码 并发 原子 atomiclong

本文主要是介绍【Java并发】原子类源码分析之AtomicLong，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！

JDK1.8

// 大部分和AtomicInteger没有太多差别，只标记不同的地方
public class AtomicLong extends Number implements java.io.Serializable {private static final long serialVersionUID = 1927816293512124184L;// setup to use Unsafe.compareAndSwapLong for updates// 通过unsafe来进行更新赋值private static final Unsafe unsafe = Unsafe.getUnsafe();private static final long valueOffset;/*** Records whether the underlying JVM supports lockless* compareAndSwap for longs. While the Unsafe.compareAndSwapLong* method works in either case, some constructions should be* handled at Java level to avoid locking user-visible locks.*/// 这里VM_SUPPORTS_LONG_CAS是一个静态变量，加载时调用VMSupportsCS8方法// VMSupportsCS8判断当前的JVM是否支持无锁的CAS，只调用一次并缓存下来static final boolean VM_SUPPORTS_LONG_CAS = VMSupportsCS8();/*** Returns whether underlying JVM supports lockless CompareAndSet* for longs. Called only once and cached in VM_SUPPORTS_LONG_CAS.*/private static native boolean VMSupportsCS8();static {try {valueOffset = unsafe.objectFieldOffset(AtomicLong.class.getDeclaredField("value"));} catch (Exception ex) { throw new Error(ex); }}private volatile long value;/*** Creates a new AtomicLong with the given initial value.** @param initialValue the initial value*/public AtomicLong(long initialValue) {value = initialValue;}/*** Creates a new AtomicLong with initial value {@code 0}.*/public AtomicLong() {}/*** Gets the current value.** @return the current value*/public final long get() {return value;}/*** Sets to the given value.** @param newValue the new value*/public final void set(long newValue) {value = newValue;}/*** Eventually sets to the given value.** @param newValue the new value* @since 1.6*/public final void lazySet(long newValue) {unsafe.putOrderedLong(this, valueOffset, newValue);}/*** Atomically sets to the given value and returns the old value.** @param newValue the new value* @return the previous value*/public final long getAndSet(long newValue) {return unsafe.getAndSetLong(this, valueOffset, newValue);}/*** Atomically sets the value to the given updated value* if the current value {@code ==} the expected value.** @param expect the expected value* @param update the new value* @return {@code true} if successful. False return indicates that* the actual value was not equal to the expected value.*/public final boolean compareAndSet(long expect, long update) {return unsafe.compareAndSwapLong(this, valueOffset, expect, update);}/*** Atomically sets the value to the given updated value* if the current value {@code ==} the expected value.** <p><a href="package-summary.html#weakCompareAndSet">May fail* spuriously and does not provide ordering guarantees</a>, so is* only rarely an appropriate alternative to {@code compareAndSet}.** @param expect the expected value* @param update the new value* @return {@code true} if successful*/public final boolean weakCompareAndSet(long expect, long update) {return unsafe.compareAndSwapLong(this, valueOffset, expect, update);}/*** Atomically increments by one the current value.** @return the previous value*/public final long getAndIncrement() {return unsafe.getAndAddLong(this, valueOffset, 1L);}/*** Atomically decrements by one the current value.** @return the previous value*/public final long getAndDecrement() {return unsafe.getAndAddLong(this, valueOffset, -1L);}/*** Atomically adds the given value to the current value.** @param delta the value to add* @return the previous value*/public final long getAndAdd(long delta) {return unsafe.getAndAddLong(this, valueOffset, delta);}/*** Atomically increments by one the current value.** @return the updated value*/public final long incrementAndGet() {return unsafe.getAndAddLong(this, valueOffset, 1L) + 1L;}/*** Atomically decrements by one the current value.** @return the updated value*/public final long decrementAndGet() {return unsafe.getAndAddLong(this, valueOffset, -1L) - 1L;}/*** Atomically adds the given value to the current value.** @param delta the value to add* @return the updated value*/public final long addAndGet(long delta) {return unsafe.getAndAddLong(this, valueOffset, delta) + delta;}/*** Atomically updates the current value with the results of* applying the given function, returning the previous value. The* function should be side-effect-free, since it may be re-applied* when attempted updates fail due to contention among threads.** @param updateFunction a side-effect-free function* @return the previous value* @since 1.8*/public final long getAndUpdate(LongUnaryOperator updateFunction) {long prev, next;do {prev = get();next = updateFunction.applyAsLong(prev);} while (!compareAndSet(prev, next));return prev;}/*** Atomically updates the current value with the results of* applying the given function, returning the updated value. The* function should be side-effect-free, since it may be re-applied* when attempted updates fail due to contention among threads.** @param updateFunction a side-effect-free function* @return the updated value* @since 1.8*/public final long updateAndGet(LongUnaryOperator updateFunction) {long prev, next;do {prev = get();next = updateFunction.applyAsLong(prev);} while (!compareAndSet(prev, next));return next;}/*** Atomically updates the current value with the results of* applying the given function to the current and given values,* returning the previous value. The function should be* side-effect-free, since it may be re-applied when attempted* updates fail due to contention among threads.  The function* is applied with the current value as its first argument,* and the given update as the second argument.** @param x the update value* @param accumulatorFunction a side-effect-free function of two arguments* @return the previous value* @since 1.8*/public final long getAndAccumulate(long x,LongBinaryOperator accumulatorFunction) {long prev, next;do {prev = get();next = accumulatorFunction.applyAsLong(prev, x);} while (!compareAndSet(prev, next));return prev;}/*** Atomically updates the current value with the results of* applying the given function to the current and given values,* returning the updated value. The function should be* side-effect-free, since it may be re-applied when attempted* updates fail due to contention among threads.  The function* is applied with the current value as its first argument,* and the given update as the second argument.** @param x the update value* @param accumulatorFunction a side-effect-free function of two arguments* @return the updated value* @since 1.8*/public final long accumulateAndGet(long x,LongBinaryOperator accumulatorFunction) {long prev, next;do {prev = get();next = accumulatorFunction.applyAsLong(prev, x);} while (!compareAndSet(prev, next));return next;}/*** Returns the String representation of the current value.* @return the String representation of the current value*/public String toString() {return Long.toString(get());}/*** Returns the value of this {@code AtomicLong} as an {@code int}* after a narrowing primitive conversion.* @jls 5.1.3 Narrowing Primitive Conversions*/public int intValue() {return (int)get();}/*** Returns the value of this {@code AtomicLong} as a {@code long}.*/public long longValue() {return get();}/*** Returns the value of this {@code AtomicLong} as a {@code float}* after a widening primitive conversion.* @jls 5.1.2 Widening Primitive Conversions*/public float floatValue() {return (float)get();}/*** Returns the value of this {@code AtomicLong} as a {@code double}* after a widening primitive conversion.* @jls 5.1.2 Widening Primitive Conversions*/public double doubleValue() {return (double)get();}}

 

这篇关于【Java并发】原子类源码分析之AtomicLong的文章就介绍到这儿，希望我们推荐的文章对编程师们有所帮助！


http://www.chinasem.cn/article/1120566。

相关文章

JVM 的类初始化机制

JVM 的类初始化机制

前言 当你在 Java 程序中new对象时，有没有考虑过 JVM 是如何把静态的字节码（byte code）转化为运行时对象的呢，这个问题看似简单，但清楚的同学相信也不会太多，这篇文章首先介绍 JVM 类初始化的机制，然后给出几个易出错的实例来分析，帮助大家更好理解这个知识点。 JVM 将字节码转化为运行时对象分为三个阶段，分别是：loading 、Linking、initialization
阅读更多...
Spring Security 基于表达式的权限控制

Spring Security 基于表达式的权限控制

前言 spring security 3.0已经可以使用spring el表达式来控制授权，允许在表达式中使用复杂的布尔逻辑来控制访问的权限。 常见的表达式 Spring Security可用表达式对象的基类是SecurityExpressionRoot。 表达式描述hasRole([role])用户拥有制定的角色时返回true （Spring security默认会带有ROLE_前缀）,去
阅读更多...
浅析Spring Security认证过程

浅析Spring Security认证过程

类图 为了方便理解Spring Security认证流程，特意画了如下的类图，包含相关的核心认证类 概述 核心验证器 AuthenticationManager 该对象提供了认证方法的入口，接收一个Authentiaton对象作为参数; public interface AuthenticationManager {Authentication authenticate(Authenti
阅读更多...
Spring Security--Architecture Overview

Spring Security--Architecture Overview

1 核心组件 这一节主要介绍一些在Spring Security中常见且核心的Java类，它们之间的依赖，构建起了整个框架。想要理解整个架构，最起码得对这些类眼熟。 1.1 SecurityContextHolder SecurityContextHolder用于存储安全上下文（security context）的信息。当前操作的用户是谁，该用户是否已经被认证，他拥有哪些角色权限…这些都被保
阅读更多...
Spring Security基于数据库验证流程详解

Spring Security基于数据库验证流程详解

Spring Security 校验流程图 相关解释说明（认真看哦） AbstractAuthenticationProcessingFilter 抽象类 /*** 调用 #requiresAuthentication(HttpServletRequest, HttpServletResponse) 决定是否需要进行验证操作。* 如果需要验证，则会调用 #attemptAuthentica
阅读更多...
Spring Security 从入门到进阶系列教程

Spring Security 从入门到进阶系列教程

Spring Security 入门系列 《保护 Web 应用的安全》 《Spring-Security-入门（一）：登录与退出》 《Spring-Security-入门（二）：基于数据库验证》 《Spring-Security-入门（三）：密码加密》 《Spring-Security-入门（四）：自定义-Filter》 《Spring-Security-入门（五）：在 Sprin
阅读更多...
Java架构师知识体认识

Java架构师知识体认识

源码分析 常用设计模式 Proxy代理模式Factory工厂模式Singleton单例模式Delegate委派模式Strategy策略模式Prototype原型模式Template模板模式 Spring5 beans 接口实例化代理Bean操作 Context Ioc容器设计原理及高级特性Aop设计原理Factorybean与Beanfactory Transaction 声明式事物
阅读更多...
Java进阶13讲__第12讲_1/2

Java进阶13讲__第12讲_1/2

多线程、线程池 1.  线程概念 1.1  什么是线程 1.2  线程的好处 2.   创建线程的三种方式 注意事项 2.1  继承Thread类 2.1.1 认识  2.1.2  编码实现  package cn.hdc.oop10.Thread;import org.slf4j.Logger;import org.slf4j.LoggerFactory
阅读更多...
性能分析之MySQL索引实战案例

性能分析之MySQL索引实战案例

文章目录 一、前言二、准备三、MySQL索引优化四、MySQL 索引知识回顾五、总结 一、前言 在上一讲性能工具之 JProfiler 简单登录案例分析实战中已经发现SQL没有建立索引问题，本文将一起从代码层去分析为什么没有建立索引？ 开源ERP项目地址：https://gitee.com/jishenghua/JSH_ERP 二、准备 打开IDEA找到登录请求资源路径位置
阅读更多...
JAVA智听未来一站式有声阅读平台听书系统小程序源码

JAVA智听未来一站式有声阅读平台听书系统小程序源码

智听未来，一站式有声阅读平台听书系统 🌟&nbsp;开篇：遇见未来，从“智听”开始 在这个快节奏的时代，你是否渴望在忙碌的间隙，找到一片属于自己的宁静角落？是否梦想着能随时随地，沉浸在知识的海洋，或是故事的奇幻世界里？今天，就让我带你一起探索“智听未来”——这一站式有声阅读平台听书系统，它正悄悄改变着我们的阅读方式，让未来触手可及！ 📚&nbsp;第一站：海量资源，应有尽有 走进“智听
阅读更多...

Copyright China编程 23002807@qq.com

沪ICP备2023033072号-2