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## net.sf.saxon.expr
Class UnionEnumeration

    java.lang.Object
      net.sf.saxon.expr.UnionEnumeration

All Implemented Interfaces:
  LookaheadIterator, SequenceIterator

public class UnionEnumeration
extends java.lang.Object
implements SequenceIterator, LookaheadIterator

An enumeration representing a nodeset that is a union of two other NodeSets.

Field Summary

Fields inherited from interface net.sf.saxon.om.SequenceIterator
`ATOMIZABLE, GROUNDED, LAST_POSITION_FINDER, LOOKAHEAD`

Constructor Summary
`UnionEnumeration(SequenceIterator p1, SequenceIterator p2, NodeOrderComparer comparer)` Create the iterator.

Method Summary
`Item` | `current()` Get the current value in the sequence (the one returned by the most recent call on next()).
`SequenceIterator` | `getAnother()` Get another SequenceIterator that iterates over the same items as the original, but which is repositioned at the start of the sequence.
`int` | `getProperties()` Get properties of this iterator, as a bit-significant integer.
`boolean` | `hasNext()` Determine whether there are more items to come.
`Item` | `next()` Get the next item in the sequence.
`int` | `position()` Get the current position.

Methods inherited from class java.lang.Object
`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Constructor Detail

### UnionEnumeration

    public UnionEnumeration(SequenceIterator p1,
                            SequenceIterator p2,
                            NodeOrderComparer comparer)
                     throws XPathException

  Create the iterator. The two input iterators must return nodes in document order for this to work.

Method Detail

### hasNext

    public boolean hasNext()

  Description copied from interface: `LookaheadIterator`
  Determine whether there are more items to come. Note that this operation is stateless and it is not necessary (or usual) to call it before calling next(). It is used only when there is an explicit need to tell if we are at the last element.

  This method must not be called unless the result of getProperties() on the iterator includes the bit setting `SequenceIterator.LOOKAHEAD`

  Specified by:
    `hasNext` in interface `LookaheadIterator`
  Returns:
    true if there are more items in the sequence

### next

    public Item next()
              throws XPathException

  Description copied from interface: `SequenceIterator`
  Get the next item in the sequence. This method changes the state of the iterator, in particular it affects the result of subsequent calls of position() and current().

  Specified by:
    `next` in interface `SequenceIterator`
  Returns:
    the next item, or null if there are no more items. Once a call on next() has returned null, no further calls should be made. The preferred action for an iterator if subsequent calls on next() are made is to return null again, and all implementations within Saxon follow this rule.
  Throws:
    `XPathException` - if an error occurs retrieving the next item

### current

    public Item current()

  Description copied from interface: `SequenceIterator`
  Get the current value in the sequence (the one returned by the most recent call on next()). This will be null before the first call of next(). This method does not change the state of the iterator.

  Specified by:
    `current` in interface `SequenceIterator`
  Returns:
    the current item, the one most recently returned by a call on next(). Returns null if next() has not been called, or if the end of the sequence has been reached.

### position

    public int position()

  Description copied from interface: `SequenceIterator`
  Get the current position. This will usually be zero before the first call on next(), otherwise it will be the number of times that next() has been called. Once next() has returned null, the preferred action is for subsequent calls on position() to return -1, but not all existing implementations follow this practice. (In particular, the EmptyIterator is stateless, and always returns 0 as the value of position(), whether or not next() has been called.)

  This method does not change the state of the iterator.

  Specified by:
    `position` in interface `SequenceIterator`
  Returns:
    the current position, the position of the item returned by the most recent call of next(). This is 1 after next() has been successfully called once, 2 after it has been called twice, and so on. If next() has never been called, the method returns zero. If the end of the sequence has been reached, the value returned will always be <= 0; the preferred value is -1.

### getAnother

    public SequenceIterator getAnother()
                                throws XPathException

  Description copied from interface: `SequenceIterator`
  Get another SequenceIterator that iterates over the same items as the original, but which is repositioned at the start of the sequence.

  This method allows access to all the items in the sequence without disturbing the current position of the iterator. Internally, its main use is in evaluating the last() function.

  This method does not change the state of the iterator.

  Specified by:
    `getAnother` in interface `SequenceIterator`
  Returns:
    a SequenceIterator that iterates over the same items, positioned before the first item
  Throws:
    `XPathException` - if any error occurs

### getProperties

    public int getProperties()

  Get properties of this iterator, as a bit-significant integer.

  Specified by:
    `getProperties` in interface `SequenceIterator`
  Returns:
    the properties of this iterator. This will be some combination of properties such as `GROUNDED`, `LAST_POSITION_FINDER`, and `LOOKAHEAD`. It is always acceptable to return the value zero, indicating that there are no known special properties. It is acceptable for the properties of the iterator to change depending on its state.

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