JAVA

singleton

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.

singleton

public final class Singleton {

  private static final Singleton INSTANCE = new Singleton();

  private Singleton() {}

  public static Singleton getInstance() { 
    return INSTANCE;
  }
}

singleton

let instance;
let counter = 0;

class Counter {
  constructor() {
    if (instance) {
      throw new Error("You can only create one instance!");
    }
    instance = this;
  }
}

const singletonCounter = Object.freeze(new Counter());
export default singletonCounter;