1、jinfo

全称：Java Configuration Info

作用：查看和调整JVM参数【实验性，不受支持】

➜ jinfo -h
Usage:
    jinfo <option> <pid>
       (to connect to a running process)

where <option> is one of:
    -flag <name>         打印指定参数的值
    -flag [+|-]<name>    启用/关闭指定参数
    -flag <name>=<value> 将指定的参数设置为指定的值
    -flags               打印VM参数
    -sysprops            打印系统属性（笔者注：系统属性打印的是System.getProperties()的结果）
    <no option>          打印VM参数及系统属性
    -? | -h | --help | -help to print this help message

2、jmap

全称：Java Memory Map

作用：展示对象内存映射或堆内存详细信息【实验性，不受支持】

➜  jmap -h
Usage:
    jmap -clstats <pid>
        to connect to running process and print class loader statistics
    jmap -finalizerinfo <pid>
        to connect to running process and print information on objects awaiting finalization
    jmap -histo[:live] <pid>
        to connect to running process and print histogram of java object heap
        if the "live" suboption is specified, only count live objects
    jmap -dump:<dump-options> <pid>
        to connect to running process and dump java heap
    jmap -? -h --help
        to print this help message

    dump-options: