org.apache.commons.collections4.iterators

Class PushbackIterator<E>

  • All Implemented Interfaces:
    Iterator<E> 

    public class PushbackIterator<E>
extends Object
implements Iterator<E>
    Decorates an iterator to support pushback of elements.

    The decorator stores the pushed back elements in a LIFO manner: the last element that has been pushed back, will be returned as the next element in a call to next().

    The decorator does not support the removal operation. Any call to remove() will result in an UnsupportedOperationException.

    Since:
    4.0

    • Constructor Detail

      • PushbackIterator

        public PushbackIterator(Iterator<? extends E> iterator)
        Constructor.
        Parameters:
        iterator - the iterator to decorate

    • Method Detail

      • pushbackIterator

        public static <E> PushbackIterator<E> pushbackIterator(Iterator<? extends E> iterator)
        Decorates the specified iterator to support one-element lookahead.

        If the iterator is already a PushbackIterator it is returned directly.

        Type Parameters:
        E - the element type
        Parameters:
        iterator - the iterator to decorate
        Returns:
        a new peeking iterator
        Throws:
        NullPointerException - if the iterator is null

      • pushback

        public void pushback(E item)
        Push back the given element to the iterator.

        Calling next() immediately afterwards will return exactly this element.

        Parameters:
        item - the element to push back to the iterator

      • hasNext

        public boolean hasNext()

      • next

        public E next()