Monday, 6 March 2017

The List Interface

The List Interface

List is an ordered Collection, sometimes called a sequence. Lists may contain duplicate elements. In addition to the operations inherited from Collection, the List interface includes operations for the following:
·         Positional access — manipulates elements based on their numerical position in the list. This includes methods such as get, set, add, addAll, and remove.
·         Search — searches for a specified object in the list and returns its numerical position. Search methods include indexOf and lastIndexOf.
·         Iteration — extends Iterator behaviour to take advantage of the list's sequential nature. The listIterator methods provide this behavior.
·         Range-view — The sublist method performs arbitrary range operations on the list.

The Java platform contains two general- purpose List implementations.
·         ArrayList, which is usually the better-performing implementation
·         LinkedList which offers better performance under certain circumstances.

ArrayList internally uses dynamic array to store the elements.
LinkedList internally uses doubly linked list to store the elements.
Manipulation with ArrayList is slow because it internally uses array. If any element is removed from the array, all the bits are shifted in memory.
Manipulation with LinkedList is faster than ArrayList because it uses doubly linked list so no bit shifting is required in memory.
ArrayList class can act as a list only because it implements List only.
LinkedList class can act as a list and queue both because it implements List and Deque interfaces.
ArrayList is better for storing and accessing data.
LinkedList is better for manipulating data.

Important methods of List Interface
Boolean add(Object obj)
Appends the specified element to the end of this list
void add(int index, Object obj)
Inserts the specified element at the specified position in this list
boolean addAll(int index, Collection c)
Inserts all elements of c into the invoking list at the index passed in the index. Returns true if the invoking list changes and returns false otherwise.
Object get(int index)
Returns the object stored at the specified index within the invoking collection.
int indexOf(Object obj)
Returns the index of the first occurrence of the specified element in this list, or -1 if this list does not contain the element.
int lastIndexOf(Object obj)
Returns the index of the last occurrence of the specified element in this list, or -1 if this list does not contain the element.
ListIterator listIterator( )
Returns an iterator to the start of the invoking list.
ListIterator listIterator(int index)
Returns an iterator to the invoking list that begins at the specified index.
Object remove(int index)
Removes the element at position index from the invoking list and returns the deleted element.
Object set(int index, Object obj)
Assigns obj to the location specified by index within the invoking list.
List subList(int start, int end)
Returns a view of the portion of this list between the specified fromIndex, inclusive, and toIndex, exclusive.

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