title: public or private, does it really matter with Android variables
body: <p>inside of a single activity, when defining components to be used only within that activity, what's the real difference between the following definitions:</p>
  
  <pre><code>Button  btnPower = null;
  //or
  private Button btnPower = null;
  //or
  public Button btnPower = null;
  
  public void somethingUsingTheButton(){
    btnPower = (Button)findViewById(R.id.btnpower_id);
  }
  </code></pre>
  
  <p>are there some "under the hood" conventions that should be thought about (garbage cleanup, memory, etc) that would suggest to always use private over public, if the entity itself is only ever going to be used inside the class it's written in?</p>