org.apache.commons.collections.iterators

## Class SingletonListIterator

- java.lang.Object
- - org.apache.commons.collections.iterators.SingletonListIterator

- All Implemented Interfaces:
    Iterator, ListIterator, ResettableIterator, ResettableListIterator

      public class SingletonListIterator
      extends Object
      implements ListIterator, ResettableListIterator

  `SingletonIterator` is an `ListIterator` over a single object instance.
  Since:
    Commons Collections 2.1
  Version:
    $Revision: 646777 $ $Date: 2008-04-10 14:33:15 +0200 (Thu, 10 Apr 2008) $
  Author:
    Stephen Colebourne, Rodney Waldhoff

- - ### Constructor Summary

    Constructors
    Constructor and Description
    `SingletonListIterator(Object object)` Constructs a new `SingletonListIterator`.

  - ### Method Summary

    Methods
    Modifier and Type | Method and Description
    --- | ---
    `void` | `add(Object obj)` Add always throws `UnsupportedOperationException`.
    `boolean` | `hasNext()` Is another object available from the iterator?
    `boolean` | `hasPrevious()` Is a previous object available from the iterator?
    `Object` | `next()` Get the next object from the iterator.
    `int` | `nextIndex()` Returns the index of the element that would be returned by a subsequent call to `next`.
    `Object` | `previous()` Get the previous object from the iterator.
    `int` | `previousIndex()` Returns the index of the element that would be returned by a subsequent call to `previous`.
    `void` | `remove()` Remove the object from this iterator.
    `void` | `reset()` Reset the iterator back to the start.
    `void` | `set(Object obj)` Set sets the value of the singleton.

    - ### Methods inherited from class java.lang.Object

      `clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

- - ### Constructor Detail

    - #### SingletonListIterator

          public SingletonListIterator(Object object)

      Constructs a new `SingletonListIterator`.
      Parameters:
        `object` - the single object to return from the iterator

  - ### Method Detail

    - #### hasNext

          public boolean hasNext()

      Is another object available from the iterator?

      This returns true if the single object hasn't been returned yet.

      Specified by:
        `hasNext` in interface `Iterator`
      Specified by:
        `hasNext` in interface `ListIterator`
      Returns:
        true if the single object hasn't been returned yet

    - #### hasPrevious

          public boolean hasPrevious()

      Is a previous object available from the iterator?

      This returns true if the single object has been returned.

      Specified by:
        `hasPrevious` in interface `ListIterator`
      Returns:
        true if the single object has been returned

    - #### nextIndex

          public int nextIndex()

      Returns the index of the element that would be returned by a subsequent call to `next`.
      Specified by:
        `nextIndex` in interface `ListIterator`
      Returns:
        0 or 1 depending on current state.

    - #### previousIndex

          public int previousIndex()

      Returns the index of the element that would be returned by a subsequent call to `previous`. A return value of -1 indicates that the iterator is currently at the start.
      Specified by:
        `previousIndex` in interface `ListIterator`
      Returns:
        0 or -1 depending on current state.

    - #### next

          public Object next()

      Get the next object from the iterator.

      This returns the single object if it hasn't been returned yet.

      Specified by:
        `next` in interface `Iterator`
      Specified by:
        `next` in interface `ListIterator`
      Returns:
        the single object
      Throws:
        `NoSuchElementException` - if the single object has already been returned

    - #### previous

          public Object previous()

      Get the previous object from the iterator.

      This returns the single object if it has been returned.

      Specified by:
        `previous` in interface `ListIterator`
      Returns:
        the single object
      Throws:
        `NoSuchElementException` - if the single object has not already been returned

    - #### remove

          public void remove()

      Remove the object from this iterator.
      Specified by:
        `remove` in interface `Iterator`
      Specified by:
        `remove` in interface `ListIterator`
      Throws:
        `IllegalStateException` - if the `next` or `previous` method has not yet been called, or the `remove` method has already been called after the last call to `next` or `previous`.

    - #### add

          public void add(Object obj)

      Add always throws `UnsupportedOperationException`.
      Specified by:
        `add` in interface `ListIterator`
      Throws:
        `UnsupportedOperationException` - always

    - #### set

          public void set(Object obj)

      Set sets the value of the singleton.
      Specified by:
        `set` in interface `ListIterator`
      Parameters:
        `obj` - the object to set
      Throws:
        `IllegalStateException` - if `next` has not been called or the object has been removed

    - #### reset

          public void reset()

      Reset the iterator back to the start.
      Specified by:
        `reset` in interface `ResettableIterator`
      Specified by:
        `reset` in interface `ResettableListIterator`

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