Should a singleton be static?
The Singleton class does not require you to use the static keyword everywhere. Static class objects cannot be passed as parameters to other methods whereas we can pass instances of a singleton as a parameter to another method.
Why you should not use singleton?
By using singletons in your project, you start to create technical debt. Singletons tend to spread like a virus because it’s so easy to access them. It’s difficult to keep track of where they’re used and getting rid of a singleton can be a refactoring nightmare in large or complex projects.
What is difference between singleton and static?
Singleton’s are instantiated, it’s just there’s only one instance ever instantiated, hence the single in Singleton. A static class can’t be instantiated by anything other than itself. Main differences are: Singleton has an instance/object while static class is a bunch of static methods.
How is singleton pattern violates single responsibility principle?
According to the Single Responsibility Principle, each class should have just one responsibility – just one reason to change. Clearly, Singleton pattern is violating this principle. Instead of clear separation of concerns, the class has two distinct responsibilities – the first is making sure that only one instance can be created.
When to use a singleton or static class?
That means, if it’s managing shared state, or if it’s changing the state of parameters, then it should be a regular class where the Factory hands out a single shared instance. A purely static class that manages shared state becomes a really hard problem for testing.
Are there any acceptable reasons to use a singleton?
On my quest for the truth I discovered that there are actually very few “acceptable” reasons to use a Singleton. One reason that tends to come up over and over again on the internets is that of a “logging” class (which you mentioned).
What are the drawbacks of using a singleton in Java?
Because of that, Singleton tends to be overused despite its many drawbacks, which are not even mentioned in the original book. The basic implementation of Singleton in Java is very simple: Make the constructor private, so there is no way to instantiate the class from the outside. Store the instance in a private static field.