JVM CLI

JVM Command-Line Tools

Every JDK ships with a set of diagnostic and management command-line tools that live inside the bin/ directory. Because they travel with the runtime, they are the first tools you should reach for when a Java process misbehaves: they cost nothing, require no agent or instrumentation, and work almost everywhere.

These tools talk to a running JVM through the Java Attach API (the same mechanism the jcmd, jps and jinfo tools use), or operate directly on saved artifacts such as heap dumps and thread dumps. Mastering a handful of them covers most day-to-day diagnosis: finding a process (jps), dumping threads (jstack), sampling the heap (jmap), inspecting flags (jinfo) and triggering diagnostics (jcmd).

Below is every bundled tool worth knowing, with the commands that actually matter.

What you'll find here: See what's running: jps, jcmd -l · Trigger diagnostics & dump threads/heaps: jcmd, jfr · Inspect live statistics: jstat, jinfo · Capture thread and heap artifacts for offline analysis

JVM CLI tools

jcmd
Sends diagnostic commands to a running JVM: heap dumps, thread dumps, JFR start/stop, GC.run, VM.system_properties and hundreds of others.
bundled-jdkOracle Free Usebundled with JDK
jps
Lists running Java processes and their VM identifiers (the `jps -lv` one-liner is how you map a PID to a JVM and its command line).
bundled-jdkOracle Free Usebundled with JDK
jstat
Prints live JVM statistics — GC counts and times, class-loading and compilation rates — in a single line, perfect for quick sampling in a loop.
bundled-jdkOracle Free Usebundled with JDK
jmap
Prints a process's memory map and heap summary, and can dump the heap to a file (jmap -dump) for offline analysis in Eclipse MAT.
bundled-jdkOracle Free Usebundled with JDK
jstack
Dumps the thread stacks of a running JVM to stdout or a file, the raw material for deadlock and hang analysis.
bundled-jdkOracle Free Usebundled with JDK
jinfo
Prints or changes system properties and JVM flags of a running process (update a flag that is mutable at runtime, or read what a process actually started with).
bundled-jdkOracle Free Usebundled with JDK
java -XX:StartFlightRecording / jfr
Java Flight Recorder: records profiling events (CPU, allocations, GC, locks, exceptions) with low overhead; `jfr` reads and prints .jfr recordings after the fact.
bundled-jdkOracle Free Usebundled with JDK
jshell
The Java REPL introduced in JDK 9, for trying snippets and exploring APIs interactively before putting them in a file.
bundled-jdkOracle Free Usebundled with JDK
javap
The class-file disassembler: shows class signatures, constant pools, and bytecode, invaluable for understanding what the compiler actually emitted.
bundled-jdkOracle Free Usebundled with JDK
jlink
Assembles a custom, minimal JVM runtime image with only the modules your application needs; the backbone of small 'slim' Java distributions.
bundled-jdkOracle Free Usebundled with JDK
jdb
The Java Debugger, a command-line debugging client that attaches to a JVM started with debugging enabled. Functional but clunky; most reach for an IDE debugger.
bundled-jdkOracle Free Usebundled with JDK
jhsdb
The HotSpot debugger, a post-mortem and live forensics tool that can inspect a crashed or hung JVM via its SA (Serviceability Agent) internals.
bundled-jdkOracle Free Usebundled with JDK

In-depth guides in this category

jcmd
jcmd examples and reference: list commands, capture heap and thread dumps, start and stop Java Flight Recorder, force GC and inspect flags.
Java Flight Recorder (JFR)
Java Flight Recorder guide: start recordings with -XX:StartFlightRecording, manage them with jcmd JFR.*, and read .jfr files with the jfr command and JDK Mission Control.
jmap
jmap examples: print heap summaries and memory maps, capture a heap dump for Eclipse MAT, and understand jmap -histo output on a live JVM.
jstack
jstack examples: dump thread stacks from a live JVM, find deadlocks and blocks, capture two-dump timing for hang analysis, and use the -l lock option.
jstat
jstat examples: sample live GC counts and times, class-loading and JIT stats from a running JVM with -gcutil, -gc, -class and interval loops.