java.lang.Object
- net.sf.saxon.tree.iter.SingletonIterator

All Implemented Interfaces:

java.io.Closeable, java.lang.AutoCloseable, LastPositionFinder, FocusIterator, SequenceIterator, GroundedIterator, LookaheadIterator, ReversibleIterator

Direct Known Subclasses:

ReportingSingletonIterator, SingleAtomicIterator
```
public class SingletonIterator
extends java.lang.Object
implements SequenceIterator, FocusIterator, ReversibleIterator, LastPositionFinder, GroundedIterator, LookaheadIterator
```
SingletonIterator: an iterator over a sequence exactly one value

Constructor Summary

Constructors
Constructor Description

SingletonIterator(Item value)
Constructor

Method Summary

All Methods Static Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`void`	`close()`	Close the iterator.
`Item`	`current()`	Get the current value in the sequence (the one returned by the most recent call on next()).
`int`	`getLength()`	Get the position of the last item in the sequence
`GroundedValue`	`getResidue()`	Return a GroundedValue containing all the remaining items in the sequence returned by this SequenceIterator, starting at the current position.
`SingletonIterator`	`getReverseIterator()`	Get a new SequenceIterator that returns the same items in reverse order.
`Item`	`getValue()`
`boolean`	`hasNext()`	Determine whether there are more items to come.
`boolean`	`isActuallyGrounded()`	Ask if the iterator is actually grounded.
`static SequenceIterator`	`makeIterator(Item item)`	Factory method.
`GroundedValue`	`materialize()`	Return a Value containing all the items in the sequence returned by this SequenceIterator
`Item`	`next()`	Get the next item in the sequence.
`int`	`position()`	Get the current position.
`boolean`	`supportsGetLength()`	Ask whether this iterator supports use of the `LastPositionFinder.getLength()` method.
`boolean`	`supportsHasNext()`	Ask whether the hasNext() method can be called.

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

- Constructor Detail
  - SingletonIterator
```
public SingletonIterator(Item value)
```
    Constructor
    
    Parameters:
    
    value - the item to iterate over. Must not be null.
- Method Detail
  - makeIterator
```
public static SequenceIterator makeIterator(Item item)
```
    Factory method.
    
    Parameters:
    
    item - the item to iterate over
    
    Returns:
    
    a SingletonIterator over the supplied item, or an EmptyIterator if the supplied item is null.
  - supportsHasNext
```
public boolean supportsHasNext()
```
    Description copied from interface: LookaheadIterator
    
    Ask whether the hasNext() method can be called. This method must be called before calling hasNext(), because some iterators implement this interface, but only support look-ahead under particular circumstances (this is usually because they delegate to another iterator)
    
    Specified by:
    
    supportsHasNext in interface LookaheadIterator
    
    Returns:
    
    true if the LookaheadIterator.hasNext() method is available
  - hasNext
```
public boolean hasNext()
```
    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.
    
    Specified by:
    
    hasNext in interface LookaheadIterator
    
    Returns:
    
    true if there are more items
  - next
```
public Item next()
```
    Description copied from interface: SequenceIterator
    
    Get the next item in the sequence. This method changes the state of the iterator.
    
    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.
  - current
```
public Item current()
```
    Description copied from interface: FocusIterator
    
    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 FocusIterator
    
    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: FocusIterator
    
    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 FocusIterator
    
    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.
  - close
```
public void close()
```
    Description copied from interface: SequenceIterator
    
    Close the iterator. This indicates to the supplier of the data that the client does not require any more items to be delivered by the iterator. This may enable the supplier to release resources. After calling close(), no further calls on the iterator should be made; if further calls are made, the effect of such calls is undefined.
    For example, the iterator returned by the unparsed-text-lines() function has a close() method that causes the underlying input stream to be closed, whether or not the file has been read to completion.
    
    Closing an iterator is important when the data is being "pushed" in another thread. Closing the iterator terminates that thread and means that it needs to do no additional work. Indeed, failing to close the iterator may cause the push thread to hang waiting for the buffer to be emptied.
    
    Closing an iterator is not necessary if the iterator is read to completion: if a call on SequenceIterator.next() returns null, the iterator will be closed automatically. An explicit call on SequenceIterator.close() is needed only when iteration is abandoned prematurely.
    
    It is not possible to guarantee that an iterator that is not read to completion or will be closed. For example, if a lazy-evaluated variable $var is passed to a user-written function, the function may access $var[1] only; we have no way of knowing whether further items will be read. For this reason, any SequenceIterator that holds resources which need to be closed should use the Cleaner mechanism. The Configuration holds a Cleaner, and resources held by a SequenceIterator should be registered with the Cleaner; if the SequenceIterator is then garbage-collected without being closed, the Cleaner will ensure that the underlying resources are closed. (An example of a SequenceIterator that uses this mechanism is the UnparsedTextIterator).
    
    Specified by:
    
    close in interface java.lang.AutoCloseable
    
    Specified by:
    
    close in interface java.io.Closeable
    
    Specified by:
    
    close in interface SequenceIterator
  - supportsGetLength
```
public boolean supportsGetLength()
```
    Description copied from interface: LastPositionFinder
    
    Ask whether this iterator supports use of the LastPositionFinder.getLength() method. This method should always be called before calling LastPositionFinder.getLength(), because an iterator that implements this interface may support use of LastPositionFinder.getLength() in some situations and not in others
    
    Specified by:
    
    supportsGetLength in interface LastPositionFinder
    
    Returns:
    
    true if the LastPositionFinder.getLength() method can be called to determine the length of the underlying sequence.
  - getLength
```
public int getLength()
```
    Description copied from interface: FocusIterator
    
    Get the position of the last item in the sequence
    
    Specified by:
    
    getLength in interface FocusIterator
    
    Specified by:
    
    getLength in interface LastPositionFinder
    
    Returns:
    
    the position of the last item
  - isActuallyGrounded
```
public boolean isActuallyGrounded()
```
    Description copied from interface: GroundedIterator
    
    Ask if the iterator is actually grounded. This method must be called before calling GroundedIterator.materialize() or GroundedIterator.getResidue(), because the iterator might be grounded under some conditions and not others (usually when it delegates to another iterator)
    
    Specified by:
    
    isActuallyGrounded in interface GroundedIterator
    
    Returns:
    
    true if this iterator is grounded
  - getReverseIterator
```
public SingletonIterator getReverseIterator()
```
    Description copied from interface: ReversibleIterator
    
    Get a new SequenceIterator that returns the same items in reverse order. If this SequenceIterator is an AxisIterator, then the returned SequenceIterator must also be an AxisIterator.
    
    Specified by:
    
    getReverseIterator in interface ReversibleIterator
    
    Returns:
    
    an iterator over the items in reverse order
  - getValue
```
public Item getValue()
```
  - materialize
```
public GroundedValue materialize()
```
    Return a Value containing all the items in the sequence returned by this SequenceIterator
    
    Specified by:
    
    materialize in interface GroundedIterator
    
    Returns:
    
    the corresponding Value. If the value is a closure or a function call package, it will be evaluated and expanded.
  - getResidue
```
public GroundedValue getResidue()
```
    Description copied from interface: GroundedIterator
    
    Return a GroundedValue containing all the remaining items in the sequence returned by this SequenceIterator, starting at the current position. This should be an "in-memory" value, not a Closure. This method does not change the state of the iterator (in particular, it does not consume the iterator).
    
    Specified by:
    
    getResidue in interface GroundedIterator
    
    Returns:
    
    the corresponding Value

Class SingletonIterator

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Constructor Detail

SingletonIterator

Method Detail

makeIterator

supportsHasNext

hasNext

next

current

position

close

supportsGetLength

getLength

isActuallyGrounded

getReverseIterator

getValue

materialize

getResidue