What is the importance of jcmd tool in Java 9?-javaTutorial-php.cn

jcmd工具在Java 9中的重要性是什么？

"jcmd" is the JVMDiagnostictool, which is a command line tool used to target a given JVM locally Run diagnostic commands on the machine. This tool is included in the JDK installation starting from versionJava 7and can be represented by the "%java_home%\bin\jcmd.exe" program file. If we include the "%java_home%\bin" directory in the environment variable "path", we can run the "jcmd -h" command to see the complete list of all directories. Options are as follows

C:\Users\User>jcmd -h Usage: jcmd or: jcmd -l or: jcmd -h command must be a valid jcmd command for the selected jvm. Use the command "help" to see which commands are available. If the pid is 0, commands will be sent to all Java processes. The main class argument will be used to match (either partially or fully) the class used to start Java. If no options are given, lists Java processes (same as -l). PerfCounter.print display the counters exposed by this process -f read and execute commands from the file -l list JVM processes on the local machine -h this help

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Example

public class JCmdToolTest { public static void main(String args[]) { Runtime runtime = Runtime.getRuntime(); System.out.println("Free memory: " + runtime.freeMemory()); System.out.println("Total memory: " + runtime.totalMemory()); try { Thread.sleep(5000); } catch(InterruptedException e) { } } }

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Output

Free memory: 65454560 Total memory: 67108864

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##We can use the "

jcmd -l" command line Output all running JVM machines locally and use thePIDor classmainin the output to identify the JVM.

C:\Users\User>jcmd -l 6108 jdk.jcmd/sun.tools.jcmd.JCmd -l

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