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();
    }
}