10/30/2022 0 Comments Deadlock in javaDEADLOCK IN JAVA HOW TOThat's all about how to avoid deadlock in Java. So, if thread A acquires a lock on Integer object, thread B will not proceed until thread A releases Integer lock, same way thread A will not be blocked even if thread B holds String lock because now thread B will not expect thread A to release Integer lock to proceed further. Now there would not be any deadlock because both methods are accessing lock on Integer and String class literal in the same order. * both will solve the problem, as long as both method are requesting lock * Both method are now requesting lock in same order, Here is my fixed version, which avoids deadlock by a voiding circular wait with no preemption, one of the four conditions which need for deadlock. DEADLOCK IN JAVA CODEIf you have looked above code carefully, then you may have figured out that real reason for the deadlock is not multiple threads but the way they are requesting a lock, if you provide ordered access then the problem will be resolved. Now the interviewer comes to the final part, one of the most important in my view How do you fix a deadlock in code? Or How to avoid deadlock in Java? The idea is that you should know the right way to use common concurrent patterns, and if you are not familiar with them then Applying Concurrency and Multi-threading to Common Java Patterns by Jose Paumard is a good starting point to learn. Since no thread is willing to give up, there is a deadlock, and the Java program is stuck. You can see that Thread 1 wants the lock on object 2 which is held by Thread 2, and Thread 2 wants a lock on Object 1 which is held by Thread 1. * and other holds Integer lock and they wait for each other, forever. * This creates potential deadlock, if one thread holds String lock * This method also requests same two lock but in exactly println( "Aquired lock on Integer.class object") println( "Aquired lock on String.class object") * This method request two locks, first String and then Integer * Java program to create a deadlock by imposing circular wait. Once you answer the earlier question, they may ask you to write code which will result in a deadlock in Java? Write a Java program that will result in deadlock? It's based on the classic Java Concurrency in Practice book by Brian Goetz, which is a recommended reading for every Java developer. I also suggest you join the Java Concurrency in Practice Bundle by Heinz Kabutz, one of the most advanced course material to master concurrency and multi-threading in Java. An advanced practical course to learn more about Java thread dumps, and familiarize you with other popular advanced troubleshooting tools. If you are interested to learn about troubleshooting tools and processes to analyze your thread dump, I suggest you take a look at Analyzing Java Thread Dumps course on Pluralsight by Uriah Levy. You can analyze that thread dump with using tools like fastthread.io which allows you to upload your thread dump and analyze it.Īnother way is to use the jConsole/VisualVM, it will show you exactly which threads are getting locked and on which object. Though this could have many answers, my version is first I would look at the code if I see a nested synchronized block or calling one synchronized method from other, or trying to get a lock on a different object then there is a good chance of deadlock if a developer is not very careful.Īnother way is to find it when you actually get dead-locked while running the application, try to take a thread dump, in Linux you can do this by the command "kill -3", this will print status of all threads in an application log file, and you can see which thread is locked on which object. It's an advanced course to become an expert in Multithreading, concurrency, and Parallel programming in Java with a strong emphasis on high performance It will only happen in the case of multitasking or multi-threading.ītw, if you are serious about mastering Java multi-threading and concurrency then I also suggest you take a look at the Java Multithreading, Concurrency, and Performance Optimization course by Michael Pogrebinsy on Udemy. Interview questions start with, " What is a deadlock?" The answer is simple when two or more threads are waiting for each other to release the resource they need (lock) and get stuck for infinite time, the situation is called deadlock. Even though the problem looks very basic but most of the Java developers get stuck once you start going deep. How to avoid deadlock in Java? Is one of the popular Java interview question and flavor of the season for multi-threading, asked mostly at a senior level with lots of follow up questions.
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