Iterator
Iterator enables you to cycle through a collection, obtaining or removing elements. List Iterator extends Iterator to allow bidirectional traversal of a list, and the modification of elements.
Before you can access a collection through an iterator, you must obtain one. Each of the collection classes provides an iterator() method that returns an iterator to the start of the collection. By using this iterator object, you can access each element in the collection, one element at a time.
Methods Declared by Iterator:
| SN | Methods with Description |
|---|---|
| 1 | boolean hasNext( ) |
| Returns true if there are more elements. Otherwise, returns false. | |
| 2 | Object next( ) |
| Returns the next element. Throws NoSuchElementException if there is not a next element. | |
| 3 | void remove( ) |
| Removes the current element. Throws IllegalStateException if an attempt is made to call remove( ) that is not preceded by a call to next( ). |
Methods Declared by ListIterator:
| SN | Methods with Description |
|---|---|
| 1 | void add(Object obj) |
| Inserts obj into the list in front of the element that will be returned by the next call to next( ). | |
| 2 | boolean hasNext( ) |
| Returns true if there is a next element. Otherwise, returns false. | |
| 3 | boolean hasPrevious( ) |
| Returns true if there is a previous element. Otherwise, returns false. | |
| 4 | Object next( ) |
| Returns the next element. A NoSuchElementException is thrown if there is not a next element. | |
| 5 | int nextIndex( ) |
| Returns the index of the next element. If there is not a next element, returns the size of the list. | |
| 6 | Object previous( ) |
| Returns the previous element. A NoSuchElementException is thrown if there is not a previous element. | |
| 7 | int previousIndex( ) |
| Returns the index of the previous element. If there is not a previous element, returns -1. | |
| 8 | void remove( ) |
| Removes the current element from the list. An IllegalStateException is thrown if remove( ) is called before next( ) or previous( ) is invoked. | |
| 9 | void set(Object obj) |
| Assigns obj to the current element. This is the element last returned by a call to either next( ) or previous( ). |