Observable in angular2

app.component.ts

import { Component, OnInit } from '@angular/core';
import { Observable } from 'rxjs/Observable';

import { HttpClient } from './observable';
import { IUser } from './userInterface';

@Component({
  selector: 'app-root',
  templateUrl: './app.component.html',
  styleUrls: ['./app.component.css']
})
export class AppComponent implements OnInit {
  debugger;
  public users: IUser[];

  constructor(
    public client: HttpClient
  ) {
  }

  public ngOnInit() { 
    this.client.fetchUsers().subscribe((users: IUser[]) => {
      this.users = users;
    });
  }
}

Observable.ts

import { Observable } from "rxjs/Observable";
import { Injectable } from "@angular/core";
import { Http, Response } from "@angular/http";
import 'rxjs/add/operator/map';

@Injectable()
export class HttpClient {

    constructor(
        public http: Http
    ) {}

    public fetchUsers() {
        return this.http.get("http://localhost:8080/api/").map((res: Response) => res.json());
    }
}