- Why can’t we use static class instead of Singleton?
- What problem does Singleton solve?
- How do you break a singleton?
- How will you implement the Singleton pattern?
- What are the benefits of using the Singleton design pattern?
- Is Singleton an anti pattern?
- What are the disadvantages of Singleton pattern?
- When should you not use a singleton?
- Why Singleton is bad for testing?
- Is Singleton class thread safe?
- Why do we use Singleton pattern?
- Are Singleton patterns good?
Why can’t we use static class instead of Singleton?
Static means that it belongs to a class it is in and not to any instance.
So it cannot be a top level class.
– Static class will have all its member as static only unlike Singleton.
– It can be lazily loaded whereas static will be initialized whenever it is first loaded..
What problem does Singleton solve?
The Singleton pattern is probably the most famous and at the same time the most controversial pattern known to us. It must be also be the simplest pattern to learn and implement. Like any other pattern, Singleton exists to solve a common business problem that is ‘managing the state of a resource’.
How do you break a singleton?
Suppose you serialize an object of a singleton class. Then if you de-serialize that object it will create a new instance and hence break the singleton pattern. As you can see, hashCode of both instances is different, hence there are 2 objects of a singleton class. Thus, the class is no more singleton.
How will you implement the Singleton pattern?
To implement a Singleton pattern, we have different approaches but all of them have the following common concepts.Private constructor to restrict instantiation of the class from other classes.Private static variable of the same class that is the only instance of the class.More items…
What are the benefits of using the Singleton design pattern?
Primarily due to the fact that a singleton holds an instantiated object, whereas static classes do not, singletons have the following advantages over static classes:Singletons can implement interfaces.Singletons can be passed as parameters.Singletons can have their instances swapped out (such as for testing purposes)More items…•
Is Singleton an anti pattern?
Critics consider the singleton to be an anti-pattern in that it is frequently used in scenarios where it is not beneficial, introduces unnecessary restrictions in situations where a sole instance of a class is not actually required, and introduces global state into an application.
What are the disadvantages of Singleton pattern?
One of the main disadvantages of singletons is that they make unit testing very hard. They introduce global state to the application. The problem is that you cannot completely isolate classes dependent on singletons. When you are trying to test such a class, you inevitably test the Singleton as well.
When should you not use a singleton?
The only situation in which you should consider a singleton is when having more than one instance of already global data would actually be a logical or hardware access error….Related Links:Brittleness invoked by Global State and Singletons.Dependency Injection to Avoid Singletons.Factories and Singletons.
Why Singleton is bad for testing?
While they provide a quick and easy solution, singletons are considered bad because they make unit testing and debugging difficult. … This property allows you to substitute alternate implementations for collaborators during testing to achieve specific testing goals (think mock objects).
Is Singleton class thread safe?
Thread Safe Singleton: A thread safe singleton in created so that singleton property is maintained even in multithreaded environment. To make a singleton class thread-safe, getInstance() method is made synchronized so that multiple threads can’t access it simultaneously.
Why do we use Singleton pattern?
In Java the Singleton pattern will ensure that there is only one instance of a class is created in the Java Virtual Machine. It is used to provide global point of access to the object. In terms of practical use Singleton patterns are used in logging, caches, thread pools, configuration settings, device driver objects.
Are Singleton patterns good?
The goal of the singleton pattern is to ensure only one instance of a class is alive at any one time. That, however, is not the goal many developers have in mind when using singletons. Singletons are very much like the good things in life, they’re not bad if used in moderation.