Singleton in Android

Tip: To create singleton class In Android Studio, right click in your project and open menu:

New -> Java Class -> Choose Singleton from dropdown menu

EDIT :

The implementation of a Singleton in Android is not "safe" (see here) and you should use a library dedicated to this kind of pattern like Dagger or other DI library to manage the lifecycle and the injection.

Could you post an example from your code ?

Launch activityB and show the mString value. "Singleton" appears...

It is simple, as a java, Android also supporting singleton. -

Singleton is a part of Gang of Four design pattern and it is categorized under creational design patterns.

-> Static member : This contains the instance of the singleton class.

-> Private constructor : This will prevent anybody else to instantiate the Singleton class.

-> Static public method : This provides the global point of access to the Singleton object and returns the instance to the client calling class.

1. create private instance
2. create private constructor

3. use getInstance() of Singleton class

   public class Logger{private static Logger   objLogger;private Logger(){        //ToDo here}public static Logger getInstance(){    if (objLogger == null)   {      objLogger = new Logger();   }   return objLogger;   }}

while use singleton -

Logger.getInstance();