@Override
	public boolean contains(Object elem) {
		return indexOf(elem) != -1;
	}
Returns the index of the last occurrence of the specified element in this list, starting the search at the specified position.
If the element is not found, -1 is returned.

@param elem			element to search for
@param fromIndex		start index for search
@return				the index of the last occurrence of the specified element in this list that is less than or equal to fromIndex,
						or -1 if this list does not contain the element
@see #lastIndexOf(Object)
jphp-runtime/src/php/runtime/memory/support/IList.java