The Java Virtual Machine (JVM) provides several command-line tools for monitoring and debugging applications. These utilities offer insights into process status, runtime statistics, configuration, memory usage, and thread states.

jps: Process Status Tool

This tool lists JVM processes on the local machine. The -l option displays the full package name of the main class.

jps -l

Example output:

14224 org.jetbrains.jps.cmdline.Launcher
8528 org.jetbrains.idea.maven.server.RemoteMavenServer
236 com.example.MainApplication

jstat: Runtime Statistics Monitor

Use jstat to collect data on class loading, garbage collection, memory pools, and JIT compilation. The basic syntax is:

jstat [options] process_id [interval [count]]

To monitor garbage collection for process 236 every 250 milliseconds for 20 iterations:

jstat -gc 236 250 20

jinfo: Configuration Inspector

This utility prints JVM system properties and command-line flags for a specified process.

jinfo 236

Sample output includes Java version, system properties, and non-default VM flags like -XX:InitialHeapSize and -XX:+UseParallelGC.

jmap: Memory Map Analyzer

jmap generates heap dumps and displays memory usage details. Too show heap configuration and usage:

jmap -heap 236

The output breaks down heap regions (Eden, Survivor, Old Generation) with capacities and utilization percentages.

jstack: Thread Stack Trace Tool

For diagnosing deadlocks or high CPU usage, jstack captures thread dumps, showing each thread's stack trace.

jstack 236

Additional Tools

• jhat: Analyzes heap dump files (.hprof).
• hsdis: A library for disassembling JIT-compiled native code.

JConsole: Graphical Monitoring

Launch jconsole from the JDK's bin directory to connect to local or remote JVM processes. The interface provides real-time views of memory consumption, thread activity, class counts, and MBean attributes.