title: length field in array
body: <p>As well known in java String class there is a <code>length()</code> method (why not <code>getLength()</code>?). If we look into this method we can see: </p>
  
  <pre><code>public int length() {
      return value.length;
  }
  </code></pre>
  
  <p>and <code>value</code> is an array. Why do we access a field? I know that this field is final and nobody can change it, but still what about polymorphism? And where can I see that field? In which class? I've found <code>java.lang.reflect.Array</code>, 
  but there is no such field as <code>length</code>. </p>