add listener vs set listener
<p>What is the difference between adding a listener and setting a listener.</p>

<p>e.g.</p>

<pre><code>addTextChangedListener(textWatcher);
setOnClickListener(clickListener);
</code></pre>

<p><strong>Answer:</strong></p>

<p>After aioobe's answer i have tested this in my project. 
So we can do this.</p>

<pre><code>editText.addTextChangedListener(textWatcher1);
editText.addTextChangedListener(textWatcher2);
</code></pre>

<p>but we can't do this.(It will set only the last listener in this case clickListener2)</p>

<pre><code>button.setOnClickListener(clickListener1);
button.setOnClickListener(clickListener2);
</code></pre>

<p><strong>Another doubt</strong></p>

<p>I am not able to think any use case in which i need two textWatcher for single editText. Can anybody give such a use case. (should i ask this question as separate question?)</p>
