Package org.apache.commons.collections4.iterators

Class EmptyIterator<E>

  • Type Parameters:
    E - the type of elements returned by this iterator.
    All Implemented Interfaces:
    java.util.Iterator<E>, ResettableIterator<E>
    public class EmptyIterator<E>
extends java.lang.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

    • Constructor Summary

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

    • Method Summary

      All Methods Static Methods Instance Methods Concrete Methods Deprecated Methods 
      Modifier and Type Method Description
      void add​(E ignored)
      Deprecated.
      Will be removed in 5.0 without replacement.
      static <E> java.util.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 Detail

      • INSTANCE

        public static final java.util.Iterator INSTANCE
        Singleton instance of the iterator.
        Since:
        2.1.1 and 3.1

    • Constructor Detail

      • EmptyIterator

        protected EmptyIterator()
        Constructs a new instance.

    • Method Detail

      • emptyIterator

        public static <E> java.util.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:
        java.lang.UnsupportedOperationException - Always thrown.

      • hasNext

        public boolean hasNext()
        Always returns false, this iterator contains no elements.
        Specified by:
        hasNext in interface java.util.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 java.util.Iterator<E>
        Returns:
        Always throws IllegalStateException.
        Throws:
        java.lang.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:
        java.lang.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 java.util.Iterator<E>
        Throws:
        java.lang.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:
        java.lang.IllegalStateException - Always thrown.