Returns the index of the first occurrence of the specified element
in this list, or -1 if this list does not contain the element.
More formally, returns the lowest index {@code i} such that
<tt>(o==null ? get(i)==null : o.equals(get(i)))</tt>,
or -1 if there is no such index.
@param o element to search for
@return the index of the first occurrence of the specified element in
this list, or -1 if this list does not contain the element
Returns the index of the first occurrence of the specified element in this list, or -1 if this list does not contain the element. More formally, returns the lowest index {@code i} such that <tt>(o==null ? get(i)==null : o.equals(get(i)))</tt>, or -1 if there is no such index.
@param o element to search for @return the index of the first occurrence of the specified element in this list, or -1 if this list does not contain the element