jdk 源码List equals中巧妙处理 处理为空的情况

public boolean equals(Object o) {
    if (o == this)
     return true;
    if (!(o instanceof List))
     return false;

    ListIterator<E> e1 = listIterator();
    ListIterator e2 = ((List) o).listIterator();
    while(e1.hasNext() && e2.hasNext()) {
        E o1 = e1.next();
     Object o2 = e2.next();
     if (!(o1==null ? o2==null : o1.equals(o2)))
        return false;
    }
    return !(e1.hasNext() || e2.hasNext());
    }