Java Collection Framework

List interface

• Ordered/sequential collection.

• List can contain duplicate elements.

• List can contain multiple null elements.

• Elements can be accessed sequentially (bi-directional using Iterator) or randomly (index based).

• List enable searching (in the list)

• Implementations: ArrayList, Vector, Stack, LinkedList, etc.

  Abstract methods

  • void add(int index, E element)
  • E get(int index)
  • E set(int index, E element)
  • E remove(int index)
  • boolean addAll(int index, Collection<? extends E> c)
  • int indexOf(Object o)
  • int lastIndexOf(Object o)
  • String toString()
  • ListIterator listIterator()
  • ListIterator listIterator(int index)
  • List subList(int fromIndex, int toIndex)

• To store objects of user-defined types in the list, you must override equals() method for the objects. It is mandatory while searching operations like conatains(), indexOf(), lastIndexOf().

Iterator vs Enumeration

Enumeration

• Since Java 1.0
• Methods:
  • boolean hasMoreElements()
  • E nextElement()
• Example:

Enumeration<E> e = v.elements();
while(e.hasMoreElements()) {
    E ele = e.nextElement();
    System.out.println(ele);
}

• Enumeration behaves similar to fail-safe iterator.

Iterator