title: RxJava - Just vs From
body: <p>I'm getting the same output when using <code>Observable.just</code> vs <code>Observable.from</code> in the following case:</p>
  <pre><code> public void myfunc() {
   //swap out just for from here and i get the same results,why ?
          Observable.just(1,2,3).subscribe(new Subscriber&lt;Integer&gt;() {
              @Override
              public void onCompleted() {
                  Log.d(&quot;&quot;,&quot;all done. oncompleted called&quot;);
              }
  
              @Override
              public void onError(Throwable e) {
  
              }
  
              @Override
              public void onNext(Integer integer) {
                  Log.d(&quot;&quot;,&quot;here is my integer:&quot;+integer.intValue());
              }
          });
  
      }
  </code></pre>
  <p>I thought <code>just</code> was just supposed to emit a single item and <code>from</code> was to emit items in some sort of list.  Whats the difference ? I also noted that <code>just</code> and <code>from</code> take only a limited amount of arguments. So <code>Observable.just(1,2,3,4,5,6,7,8,-1,-2)</code> is ok but <code>Observable.just(1,2,3,4,5,6,7,8,-1,-2,-3)</code> fails. Same goes for <code>from</code>, I have to wrap it in a list or array of sorts.  I'm just curious why they can't define unlimited arguments.</p>
  <p>UPDATE: I experimented and saw that <code>just</code> does not take a array structure it just takes arguments. <code>from</code> takes a collection. so the following works for <code>from</code> but not for <code>just</code>:</p>
  <pre><code> public Observable myfunc() {
      Integer[] myints = {1,2,3,4,5,6,7,8,-1,-2,9,10,11,12,13,14,15};
     return  Observable.just(myints).flatMap(new Func1&lt;Integer, Observable&lt;Boolean&gt;&gt;() {
          @Override
          public Observable&lt;Boolean&gt; call(final Integer integer) {
              return Observable.create(new Observable.OnSubscribe&lt;Boolean&gt;() {
                  @Override
                  public void call(Subscriber&lt;? super Boolean&gt; subscriber) {
                      if(integer.intValue()&gt;2){
                          subscriber.onNext(integer.intValue()&gt;2);
  
                      }
                  }
              });
          }
      });
  
  }
  </code></pre>
  <p>I am assuming this to be the clear difference then, correct ?</p>