本文是按照自己的理解进行笔记总结，如有不正确的地方，还望大佬多多指点纠正，勿喷。

课程内容：

1、阿里巴巴Arthas调优工具详解

2、GC日志详解与调优分析

3、Class常量池与运行时常量池详解

4、字符串常量池与基本类型常量池详解

1. 阿里巴巴Arthas详解

Arthas是 Alibaba在2018年9月开源的Java诊断工具。支持JDK6+，采用命令行交互模式，可以方便的定位和诊断线上程序运行问题。Arthas官方文档十分详细，详见: https://alibaba.github.io/arthas

1.1 Arthas使用

#github下载arthas
wget https://alibaba.github.io/arthas/arthas-boot.jar
#或者Gitee下载
wget https://arthas.gitee.io/arthas-boot.jar

用java -jar运行即可，可以识别机器上所有Java进程(我们这里之前已经运行了一个Arthas测试程序，代码见下方)

package ding;import java.util.HashSet;public class Arthas {private static HashSet hashSet = new HashSet();public static void main(String[] args) {//模拟cpu过高cpuHigh();//模拟线程死锁deadThread();//不断地向HashSet集合增加数据addHashSetThread();}/*** 不断地向hashSet集合添加数据*/public static void addHashSetThread(){//初始化常量new Thread(()->{int count = 0;while (true){try {hashSet.add("count" + count);Thread.sleep(10000);count++;} catch (InterruptedException e) {e.printStackTrace();}}}).start();}public static void cpuHigh() {new Thread(()->{while (true){}}).start();}/*** 死锁*/private static void deadThread() {//创建资源Object resourceA = new Object();Object resourceB = new Object();//创建线程Thread threadA = new Thread(()->{synchronized (resourceA){System.out.println(Thread.currentThread()+"get ResourceA");try {Thread.sleep(1000);} catch (InterruptedException e) {e.printStackTrace();}System.out.println(Thread.currentThread()+"waiting get ResourceB");synchronized (resourceB){System.out.println(Thread.currentThread()+"get ResourceB");}}});Thread threadB = new Thread(()->{synchronized (resourceB){System.out.println(Thread.currentThread()+"get ResourceB");try {Thread.sleep(1000);} catch (InterruptedException e) {e.printStackTrace();}System.out.println(Thread.currentThread()+"waiting get ResourceA");synchronized (resourceB){System.out.println(Thread.currentThread()+"get ResourceA");}}});threadA.start();threadB.start();}
}