spring hibernate interview questions java revisited

Spring hibernate interview questions java revisited software#

The implementation relies on the well-specified initialization phase of execution within the Java Virtual Machine (JVM) see section 12.4 of Java Language Specification (JLS) for details. Private static final Singleton INSTANCE = new Singleton() If you guys are looking for thread safety and the combination of lazy initialization.then follow Initialization-on-demand holder idiom. I like your blog for spreading words and experience on Java Singleton multithreading issues. Anything with threading requires serious knowledge of Java multithreading concept. Writing a thread safe singleton for multithreaded environment is not a joke. In this case, class loaders can create several singleton instances from only one class. Imagin you have huge entrprise platfrom that have several class loaders. Showed singleton is only one of more thread-safe singleton realizations.Īctually this have one problem only if you have. How about static inner class with singleton instance? Javin List vs does it really necessary to make Singleton final, doesn't making constructor private will prevent it from being extended? Regarding Reflection, I think only way to prevent creating instance is throwing Exception from constructor itself. Public class Singleton also needs to be declared final, to avoid being subclassed (and, for example, instantiate a new Singleton object via reflection)

Spring hibernate interview questions java revisited software#

It's best to get this kind of knowledge as part of your work but even if you don't get there, you can supplement them by these online design pattern courses and doing some object-oriented software design exercises.

Let’s see examples of both ways to create thread-safe Singleton in Java.ītw, In order to best understand design patterns, you need to work out some scenarios, examples, etc. I personally don't prefer that way as there are many other simpler alternatives to write thread-safe singleton is available like using static field to initialize Singleton instance or using Enum as Singleton in Java. Prior to Java 5 double-checked locking mechanism is used to create a thread-safe singleton in Java which breaks if one Thread doesn't see an instance created by another thread at the same time and eventually you will end up with more than one instance of Singleton class.įrom Java 5 onwards volatile variable guarantee can be used to write thread-safe singleton by using double-checked locking pattern. In our last post, 10 Interview questions on Singleton in Java we have discussed many different questions asked on Singleton pattern, One of them was writing Thread safe singleton in Java. Singleton pattern ensures that exactly one instance of the class will remain in the Java program at any time. Singleton in Java has been a classical design pattern like Factory method pattern, or Decorator design pattern and has been used a lot even inside JDK like is an example of Singleton class. Thread safe Singleton means a Singleton class that returns exactly the same instance even if exposed to multiple threads.