一、jinfo命令格式

命令格式：

jinfo [option]

Usage:
    jinfo [option] 
        (to connect to running process)
    jinfo [option] 
        (to connect to a core file)
    jinfo [option] [server_id@]hostname>
        (to connect to remote debug server)

where  is one of:
    -flag          to print the value of the named VM flag
    -flag [+|-]    to enable or disable the named VM flag
    -flag = to set the named VM flag to the given value
    -flags               to print VM flags
    -sysprops            to print Java system properties
              to print both of the above
    -h | -help           to print this help message

二、打印所有参数

 jinfo -flags [pid]

三、查看某个参数

 四、动态修改参数

1、禁用（不过该参数不能修改）

2、启用（也遇到了不能改的）

3、来个可改的

五、查看系统属性