code: protected void beforeInsertDummies(int index, int length) {
  	if (index > size || index < 0) 
  		throw new IndexOutOfBoundsException("Index: "+index+", Size: "+size);
  	if (length > 0) {
  		ensureCapacity(size + length);
  		setSizeRaw(size + length);
  		replaceFromToWithFrom(index+length,size-1,this,index);
  	}
  }
docs: Inserts <tt>length</tt> dummy elements before the specified position into the receiver.
  Shifts the element currently at that position (if any) and
  any subsequent elements to the right.
  <b>This method must set the new size to be <tt>size()+length</tt>.
  
  @param index index before which to insert dummy elements (must be in [0,size])..
  @param length number of dummy elements to be inserted.
  @throws IndexOutOfBoundsException if <tt>index &lt; 0 || index &gt; size()</tt>.