title: Calling four api's combining together using RxJava
body: <p>I am new to RxJava</p>
  
  <p><strong>Restapi.class</strong></p>
  
  <pre><code>/************/
      @GET("app/dashboard")
      Observable&lt;CategoryHomeModel[]&gt; getCategories(@HeaderMap Map&lt;String, String&gt; headers);
  
      @GET("app/wallet/balance")
      Observable&lt;WalletBalance&gt; getWalletBalance(@HeaderMap Map&lt;String, String&gt; headers);
  
      @GET("/app/swap/myrateswaps")
      Observable&lt;SwapSettings&gt; rateMySwap(@HeaderMap Map&lt;String, String&gt; headers);
  
      @GET("/app/getsettings")
      Observable&lt;Settings&gt; getSettings(@HeaderMap Map&lt;String, String&gt; headers);
      /************/
  </code></pre>
  
  <h2>I have Four observables</h2>
  
  <pre><code>Observable&lt;CategoryHomeModel[]&gt; categoriesObservable = retrofit
              .create(Restapi.class)
              .getCategories(prepareHeaders())
              .subscribeOn(Schedulers.newThread())
              .observeOn(AndroidSchedulers.mainThread());
  
      Observable&lt;WalletBalance&gt; walletObservable = retrofit
              .create(Restapi.class)
              .getWalletBalance(prepareHeaders())
              .subscribeOn(Schedulers.newThread())
              .observeOn(AndroidSchedulers.mainThread());
  
      Observable&lt;Settings&gt; settingsObservable = retrofit
              .create(Restapi.class)
              .getSettings(prepareHeaders())
              .subscribeOn(Schedulers.newThread())
              .observeOn(AndroidSchedulers.mainThread());
  
      Observable&lt;SwapSettings&gt; ratingsObservable = retrofit
              .create(Restapi.class)
              .rateMySwap(prepareHeaders())
              .subscribeOn(Schedulers.newThread())
              .observeOn(AndroidSchedulers.mainThread());
  </code></pre>
  
  <hr>
  
  <p>How to combine all four observables into one and get the response in one place and handle all the response of all the observables together </p>
  
  <hr>
  
  <p>I found out this can be done from Merge, If so how to use the merge ?</p>