Package org.apache.commons.collections4.iterators

Class EmptyIterator<E>

java.lang.Object
org.apache.commons.collections4.iterators.EmptyIterator<E>
Type Parameters:
E - the type of elements returned by this iterator.
All Implemented Interfaces:
Iterator<E>, ResettableIterator<E>
public class EmptyIterator<E> extends Object
Provides an implementation of an empty iterator.

This class provides an implementation of an empty iterator. This class provides for binary compatibility between Commons Collections 2.1.1 and 3.1 due to issues with IteratorUtils.

Since:
2.1.1 and 3.1

  • Field Summary

    Fields
    Modifier and Type
    Field
    Description
    static final Iterator
    INSTANCE
    Singleton instance of the iterator.
    static final ResettableIterator
    RESETTABLE_INSTANCE
    Singleton instance of the iterator.

  • Constructor Summary

    Constructors
    Modifier
    Constructor
    Description
    protected
    EmptyIterator()
    Constructs a new instance.

  • Method Summary

    Modifier and Type
    Method
    Description
    void
    add(E ignored)
    Deprecated.
    Will be removed in 5.0 without replacement.
    static <E> Iterator<E>
    emptyIterator()
    Gets a typed empty iterator instance.
    boolean
    hasNext()
    Always returns false, this iterator contains no elements.
    boolean
    hasPrevious()
    Always returns false, this iterator contains no elements.
    E
    next()
    Always throws IllegalStateException, this iterator contains no elements.
    int
    nextIndex()
    Always returns 0, this iterator contains no elements.
    E
    previous()
    Always throws IllegalStateException, this iterator contains no elements.
    int
    previousIndex()
    Always returns -1, this iterator contains no elements.
    void
    remove()
    Always throws IllegalStateException, this iterator contains no elements.
    void
    reset()
    Resets the iterator back to the position at which the iterator was created.
    static <E> ResettableIterator<E>
    resettableEmptyIterator()
    Gets a typed resettable empty iterator instance.
    void
    set(E ignored)
    Always throws IllegalStateException, this iterator contains no elements.

    Methods inherited from class java.lang.Object

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

    Methods inherited from interface java.util.Iterator

    forEachRemaining

  • Field Details

  • Constructor Details

    • EmptyIterator

      protected EmptyIterator()
      Constructs a new instance.

  • Method Details

    • emptyIterator

      public static <E> Iterator<E> emptyIterator()
      Gets a typed empty iterator instance.
      Type Parameters:
      E - the element type
      Returns:
      Iterator<E>

    • resettableEmptyIterator

      public static <E> ResettableIterator<E> resettableEmptyIterator()
      Gets a typed resettable empty iterator instance.
      Type Parameters:
      E - the element type
      Returns:
      ResettableIterator<E>

    • add

      @Deprecated public void add(E ignored)
      Deprecated.
      Will be removed in 5.0 without replacement.
      Always throws UnsupportedOperationException.
      Parameters:
      ignored - ignore.
      Throws:
      UnsupportedOperationException - Always thrown.

    • hasNext

      public boolean hasNext()
      Always returns false, this iterator contains no elements.
      Specified by:
      hasNext in interface Iterator<E>
      Returns:
      Always false.

    • hasPrevious

      public boolean hasPrevious()
      Always returns false, this iterator contains no elements.
      Returns:
      Always false.

    • next

      public E next()
      Always throws IllegalStateException, this iterator contains no elements.
      Specified by:
      next in interface Iterator<E>
      Returns:
      Always throws IllegalStateException.
      Throws:
      IllegalStateException - Always thrown.

    • nextIndex

      public int nextIndex()
      Always returns 0, this iterator contains no elements.
      Returns:
      Always returns 0.

    • previous

      public E previous()
      Always throws IllegalStateException, this iterator contains no elements.
      Returns:
      Always throws IllegalStateException.
      Throws:
      IllegalStateException - Always thrown.

    • previousIndex

      public int previousIndex()
      Always returns -1, this iterator contains no elements.
      Returns:
      Always returns -1.

    • remove

      public void remove()
      Always throws IllegalStateException, this iterator contains no elements.
      Specified by:
      remove in interface Iterator<E>
      Throws:
      IllegalStateException - Always thrown.

    • reset

      public void reset()
      Description copied from interface: ResettableIterator
      Resets the iterator back to the position at which the iterator was created.
      Specified by:
      reset in interface ResettableIterator<E>

    • set

      public void set(E ignored)
      Always throws IllegalStateException, this iterator contains no elements.
      Parameters:
      ignored - ignored.
      Throws:
      IllegalStateException - Always thrown.