public abstract class AbstractList extends AbstractCollection implements List
This class provides a skeletal implementation of the List interface to minimize the effort required to implement this interface backed by a "random access" data store (such as an array). For sequential access data (such as a linked list), AbstractSequentialList should be used in preference to this class.
To implement an unmodifiable list, the programmer needs only to extend this class and provide implementations for the get(int index) and size() methods.
To implement a modifiable list, the programmer must additionally override the set(int index, Object element) method (which otherwise throws an UnsupportedOperationException. If the list is variable-size the programmer must additionally override the add(int index, Object element) and remove(int index)
The programmer should generally provide a void (no argument) and collection constructor, as per the recommendation in the Collection interface specification.
Unlike the other abstract collection implementations, the programmer does not have to provide an iterator implementation; the iterator and list iterator are implemented by this class, on top the "random access" methods:
get(int index), set(int index, Object element), set(int index, Object element), add(int index, Object element) and remove(int index).