One 、 Parameter query

 perform ：
	java -XX:+PrintFlagsFinal
 Be careful ：
	=		 Represents the default value 
	:=		 Said by JVM Or the value modified by the user 

Two 、 Parameter classification

1、 Standard parameters

-version 
-help 
-server 
-cp

2、-X Parameters （ Nonstandard ,JDK There may be changes in various versions ）

-Xint 	 Explain to perform  
-Xcomp 	 Compile it into local code for the first time  
-Xmixed  Mixed mode ,JVM Decide for yourself 

3、-XX Parameters （ Nonstandard , Relatively unstable , It is mainly used for JVM tuning ）

1）Boolean type

 Format ：
	-XX:[+-]<name> 
 Be careful ：
	+  Means to enable name attribute 
	+ -  Disable name attribute 
 Example ：
	 -XX:+UseConcMarkSweepGC 	 Means to enable CMS Type of garbage collector 
	 -XX:+UseG1GC				 Means to enable G1 Type of garbage collector  

2） Not Boolean type

 Format ：
	-XX<name>=<value>
 Be careful ：
	name The value of the property is value 
 Example ：
	-XX:MaxGCPauseMillis=500

4、 The other parameters （ Short for parameters ）

-Xms1000M	 Equivalent to 	-XX:InitialHeapSize=1000M
-Xmx1000M	 Equivalent to 	-XX:MaxHeapSize=1000M
-Xss100		 Equivalent to 	-XX:ThreadStackSize=100

3、 ... and 、 Common parameters

Four 、 Common ways to set parameters

1、 development tool ：IDEA,eclipse
2、 function jar：java -XX:+UseG1GC xxx.jar
3、Web Containers ：tomcat Script
4、 adopt jinfo Adjust something in real time java Process parameters ( The parameter is only marked manageable Of flags Can be modified in real time )