Singleton pattern implementation code example

Example 1: java singleton implementation

public class SingletonClass {
    private static final SingletonClass SINGLE_INSTANCE = new SingletonClass();
    private SingletonClass() {}
  public static SingletonClass getInstance() {
      return SINGLE_INSTANCE;
    }
}

Example 2: what is singleton design pattern

Singleton Design Pattern is basically limiting our class so that 
whoever is using that class can only create 1 instance from that class.
       
I create a private constructor which limits access to the instance of the class.
Than I create a getter method where we specify how to create&use the instance.
    - I am using JAVA Encapsulation OOP concept.

Example 3: singleton pattern

class Singleton:
    __instance = None
    def __new__(cls, *args):
        if cls.__instance is None:
            cls.__instance = object.__new__(cls, *args)
        return cls.__instance

Example 4: singleton pattern

class Singleton(object):
    __instance = None
    def __new__(cls, *args):
        if cls.__instance is None:
            cls.__instance = object.__new__(cls, *args)
        return cls.__instance