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if we talk about static variable then we difine it as The static variable can be used to refer the common property of all objects (that is not unique for each object) e.g. company name of employees,college name of students etc. The static variable gets memory only once in class area at the time of class loading.
Static variables have a property of preserving their value even after they are out of their scope! Hence, static variables preserve their previous value in their previous scope and are not initialized again in the new scope.
The static method is similar to instance or class method of a class but with the difference that the static method can be called through the name of class without creating any instance of that class. A static method is also called class method as it is related with a class and not with individual instance of the class.
Static Variables: When a variable is declared as static, then a single copy of the variable is created and shared among all objects at a class level. Static variables are, essentially, global variables. All instances of the class share the same static variable.
static fields are attached to the Class instance as a whole, which is in turn attached to the ClassLoader which loaded the class. the_instance would be unloaded when the entire ClassLoader is reclaimed. I am 90% sure this happens when Android destroys the app (not when it goes into the background, or pauses, but is completely shut down.)
So, think of it as living as long as your app runs. Is Singleton a good idea? People have different views. I think it's fine when used appropriately, myself. I don't think the answer changes much on Android. Memory usage isn't the issue per se; if you need to load a bunch of stuff in memory, that's either a problem or it isn't, regardless of whether you encapsulate the data in a Singleton.
I think static variables are OK.
This is what Android doc says:
http://developer.android.com/guide/appendix/faq/framework.html
How do I pass data between Activities/Services within a single application?
A public static field/method
An alternate way to make data accessible across Activities/Services is to use public static fields and/or methods. You can access these static fields from any other class in your application. To share an object, the activity which creates your object sets a static field to point to this object and any other activity that wants to use this object just accesses this static field.
Contrary to what other people say - it is more than ok. Granted, it has some structure to it. In the official googlesamples/android-architecture repo it is used under todo-mvp-clean (Todo app implementing MVP pattern and following Clean Architecture principles). Check out this file.
What you can see is a lot of static methods referencing singleton getters.
Modern, less error prone and convenient alternative is the Dagger DI framework.
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