How to Capture Java Thread Dumps Using JDK Tools, OS Signals, and ThreadMXBean

Thread dump is a snapshot of all thread states in a Java process, showing stack traces for diagnosing issues.

JDK provides utilities located in the bin directory, such as jstack and jcmd , which can be invoked from the command line.

jstack

jstack captures a thread dump for a given PID and prints it to the console or a file.

Basic syntax:

jstack [-l][-e] <pid>

Options:

-l : long format, prints additional lock information.

-e : extended format, prints extra thread information.

-?, -h, --help, -help : display help.

Example:

jstack 17264 > /tmp/threaddump.txt

jcmd

jcmd is a versatile command‑line tool that sends commands to a JVM.

Basic syntax:

jcmd <pid|main class> <command ...>
jcmd -l
jcmd -h

Common options include -l to list JVM processes, -?, -h, --help for help, and many JVM‑specific commands such as Thread.print , GC.heap_dump , etc.

Example:

jcmd 17264 Thread.print

Operating‑system signal

On Unix/Linux, sending kill -3 <pid> triggers a thread dump.

Redirecting output via JVM options

Use diagnostic VM options to write thread dumps to a file, e.g.:

-XX:+UnlockDiagnosticVMOptions -XX:+LogVMOutput -XX:LogFile=~/jvm.log

Programmatic generation with ThreadMXBean

The JMX ThreadMXBean can be used to dump all threads programmatically.

private static String threadDump(boolean lockedMonitors, boolean lockedSynchronizers) {
    StringBuffer threadDump = new StringBuffer(System.lineSeparator());
    ThreadMXBean threadMXBean = ManagementFactory.getThreadMXBean();
    for (ThreadInfo threadInfo : threadMXBean.dumpAllThreads(lockedMonitors, lockedSynchronizers)) {
        threadDump.append(threadInfo.toString());
    }
    return threadDump.toString();
}

The method initializes a StringBuffer , obtains the ThreadMXBean via ManagementFactory , and calls dumpAllThreads() with optional lock information.

Graphical tools

Tools such as Java Mission Control (JMC), jvisualvm, and jconsole provide visual analysis of thread dumps.

Conclusion

The article lists several ways to capture Java thread dumps: JDK command‑line tools (jstack, jcmd, JMC, jvisualvm, jconsole), OS signals (kill ‑3), and programmatic access via ThreadMXBean . It recommends using jcmd on Java 8+ for full functionality, graphical tools for visual analysis, and OS or programmatic methods in production environments without JDK tools.