Singleton Design Pattern in detail with Code and Explanation | Interview Question #java

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Singleton Design Pattern:

The singleton pattern is implemented by creating a class with a method that creates a new class instance if one does not exist. An instance already exists simply returns a reference to that object.

A single class have private constructor and static instance. In Lazy Instantiation singleton pattern creates the instance in the global access method.

A thread-safe singleton class is to make the global access method synchronized. Using this concept, a single thread can execute this method at a time. If you want huge amount of work to be done using getInstance method then it will decreased your system performance by factor of 100.

Double check locking is used to ensure that only one instance of singleton class is created.
This means we checked object is null two times that :
1) Simply check for object has already been initialized. If yes then apply second way.
2) Inside synchronized block again check for object has already been initialized.


Abstract Factory design pattern : https://youtu.be/u3LuF3t6rp0?si=3iSYHclpMWU135Mf
Factory method design pattern : https://youtu.be/0b3G-GDSobE?si=vNevAxtyggIA29Zq
Design pattern in java: https://youtu.be/45OuBdifrO0?si=a5OAR6cGcV9VqIYe


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