title: Why can not use a String to initialize a StringBuilder object?
body: <pre><code>StringBuilder sb = "asd";
  </code></pre>
  
  <p>In Java, this statement is obviously wrong. IDEs like eclipse will tell you that :</p>
  
  <blockquote>
    <p>cannot convert from String to StringBuilder</p>
  </blockquote>
  
  <p>However, a <code>String</code> object could be initialized by <code>=</code> operator.</p>
  
  <p>I'd like to know some reasons related with the <strong>memory allocation</strong>.</p>