How to create a singleton service in Angular 2?

Here is the steps to create a singleton service-

• Import the injectable member using import {Injectable} from '@angular/core';
• Import the HttpModule, Http and Response members’ as import { HttpModule, Http, Response } from '@angular/http';
• Add the decorator @Injectable()
• Export –
  export class UserService {
   constructor(private _http: Http) { }
}