Java Print Stack Trace — Complete CLI Reference, Syntax

java print stack trace is the process of outputting the call stack of an exception or current thread for debugging in Java. It is achieved via Throwable.printStackTrace(), Thread.currentThread().getStackTrace(), or the jstack CLI utility.

Syntax

# Throwable.printStackTrace() variants
public void printStackTrace()
public void printStackTrace(PrintStream s)
public void printStackTrace(PrintWriter s)

# Get stack trace as array
StackTraceElement[] elements = Thread.currentThread().getStackTrace();

# jstack CLI (JVM process)
jstack [-l] <pid>
jstack -F [-m] [-l] <pid>
jstack [-m] [-l] <executable> <core>
jstack [-m] [-l] [server_id@]<remote hostname>

Options and Flags

Usage Examples

1. Basic Exception Debugging with printStackTrace()

# Java code (in file DebugExample.java)
public class DebugExample {
    public static void main(String[] args) {
        try {
            int[] arr = new int[2];
            arr[5] = 10; // ArrayIndexOutOfBoundsException
        } catch (Throwable e) {
            e.printStackTrace();
        }
    }
}
# Compile and run
javac DebugExample.java
java DebugExample

The printStackTrace() method prints the exception class, message, and a full call stack to System.err. This is the most direct way to diagnose unhandled exceptions during development.

2. Capturing Stack Trace as a String for Logging

# Java code snippet
StringWriter sw = new StringWriter();
PrintWriter pw = new PrintWriter(sw);
e.printStackTrace(pw);
String stackTrace = sw.toString();
System.out.println("Error:n" + stackTrace);

Using printStackTrace(PrintWriter) together with StringWriter converts the stack trace into a string. This is the standard approach for inserting stack traces into log files, databases, or custom error reports without losing context.

3. Using jstack to Debug a Hung JVM Process

# Find the Java process PID
ps aux | grep java
# Force a thread dump (use -F if process is not responding)
jstack -F <pid> > /tmp/threaddump_$(date +%Y%m%d).txt
# For a live process, use -l to see lock info
jstack -l <pid>

jstack prints Java thread stacks of a running JVM. The -F flag is critical when the process is hung and does not respond normally. The output helps identify deadlocks, blocked threads, and high‑CPU threads.

Frequently Asked Questions

Thread.currentThread().getStackTrace(); // returns StackTraceElement[]

java -XX:-OmitStackTraceInFastThrow -jar app.jar

java -XX:-OmitStackTraceInFastThrow -jar myapp.jar

java -XX:-OmitStackTraceInFastThrow -version

jstack -l 12345 | grep -A 30 "main"   # thread-specific

jcmd 12345 Thread.print -l