Debug, Diagnose & Fix a Deadlock in Java | Thread Dump Analysis (jstack, jcmd, kill) | With Example
Deadlock is one of the most critical issues in Java Multithreading that can freeze your application completely.
In this video, you will learn how to DEBUG, DIAGNOSE and FIX a deadlock in Java step-by-step with a real-life example.
🚨 What you will learn:
✅ What is Deadlock in Java?
A situation where two or more threads are blocked forever waiting for each other.
✅ Write a program to get Deadlock in Java?
Watch this video
✅ How to identify a deadlock (Symptoms)
Application hang
Threads stuck or not responding
✅ Step-by-step Deadlock Debugging Process:
1. Capture Thread Dump
2. Analyze and find circular dependency
3. Trace source code
4. Apply fix
📸 Thread Dump Explained:
A thread dump is a snapshot of all thread states at a given moment.
👉 Always take at least 3 dumps (10 seconds apart) to confirm deadlock.
🛠️ Ways to capture Thread Dump:
✔ Using java commands
✔ Use jps (to get PID)
✔ Using jstack (most common)
Syntax: jstack pid then redirect to output threaddump.txt
✔ Using jcmd (modern approach)
jcmd pid Thread.print then redirect to output threaddump.txt
✔ Using kill -3 (for unresponsive apps)
kill -3 pid
for kill command output will be printed in the application log
✔ Using UI tools:
✔ VisualVM
✔ JConsole
✔ IntelliJ built-in debugger (camera icon)
💡 How to FIX Deadlock:
✔ Acquire locks in same order
✔ Use tryLock() with timeout (ReentrantLock)
✔ Avoid nested locking
✔ Use concurrent collections like ConcurrentHashMap
🎯 Perfect for:
Java Developers
Backend Engineers
Interview Preparation
Production debugging
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🔥 Pro Tip:
Deadlock debugging = Thread Dump Analysis + Lock Understanding
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Github repo link : https://tinyurl.com/deadlockdebug
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