VisualVM is a visualization tool that integrates multiple JDK command-line tools, which can provide you with powerful analysis capabilities. All of these are free! It includes command line tools including jps, jstat, jmap, jinfo, jstack, JConsole, these tools are consistent with the standard version of JDK.
jps: Similar to ps on unix, it is used to display the local java process, you can view several java programs running locally, and display their process numbers.
jstat: An extremely powerful tool for monitoring VM memory. Can be used to monitor various heap and non-heap sizes and their memory usage within VM memory.
jmap: Print out all 'objects' in the memory of a java process (using pid) (eg: those objects are generated, and their number).
jinfo: This JVM monitoring tool can output and modify the opts of the running java process.
jsatck: If the java program crashes to generate the core file, the jstack tool can be used to obtain the information of the javastack and nativestack of the core file, so that you can easily know how the java program crashes and where the problem occurs in the program.
jconsole: A javaGUI monitoring tool that can display various data in a graphical form. And can monitor the remote server VM through the remote connection.