code: public Object getContext(Class key) {
          if(key == null) {
              throw new NullPointerException();
          }
          return map.get(key);
      }
docs: Returns the context object associated with the given key.
  
  <p>The <code>ELContext</code> maintains a collection of context objects
  relevant to the evaluation of an expression. These context objects
  are used by <code>ELResolver</code>s.  This method is used to
  retrieve the context with the given key from the collection.</p>
  
  <p>By convention, the object returned will be of the type specified by
  the <code>key</code>.  However, this is not required and the key is
  used strictly as a unique identifier.</p>
  
  @param key The unique identifier that was used to associate the
  context object with this <code>ELContext</code>.
  @return The context object associated with the given key, or null
  if no such context was found.
  @throws NullPointerException if key is null.