ItemCheckingIterator

java.lang.Object
- net.sf.saxon.expr.ItemCheckingIterator

All Implemented Interfaces:

java.io.Closeable, java.lang.AutoCloseable, LastPositionFinder, SequenceIterator, LookaheadIterator
```
public class ItemCheckingIterator
extends java.lang.Object
implements SequenceIterator, LookaheadIterator, LastPositionFinder
```
ItemCheckingIterator applies a supplied function to each item in a sequence. The iterator returns the same items as the original, but has side effects (such as throwing an error) determined by the supplied callback function

Constructor Summary

Constructors
Constructor and Description
`ItemCheckingIterator(SequenceIterator base, java.util.function.Consumer<Item> action)` Construct an ItemCheckingIterator that will apply a specified DummyItemMappingFunction to each Item returned by the base iterator.

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`void`	`close()` Close the iterator.
`void`	`discharge()` Calling this method instructs the iterator to release any resources it holds, while still remaining able to deliver the remaining items in the sequence.
`int`	`getLength()` Get the last position (that is, the number of items in the sequence).
`boolean`	`hasNext()` Determine whether there are more items to come.
`Item`	`next()` Get the next item in the sequence.
`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
  - ItemCheckingIterator
```
public ItemCheckingIterator(SequenceIterator base,
                            java.util.function.Consumer<Item> action)
```
    Construct an ItemCheckingIterator that will apply a specified DummyItemMappingFunction to each Item returned by the base iterator.
    
    Parameters:
    
    base - the base iterator
    
    action - the mapping function to be applied.
- Method Detail
  - 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()
```
    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 LookaheadIterator.supportsHasNext() is true.
    
    Specified by:
    
    hasNext in interface LookaheadIterator
    
    Returns:
    
    true if there are more items in the sequence
  - 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.
  - 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.
    
    Specified by:
    
    close in interface java.io.Closeable
    
    Specified by:
    
    close in interface java.lang.AutoCloseable
    
    Specified by:
    
    close in interface SequenceIterator
  - discharge
```
public void discharge()
```
    Description copied from interface: SequenceIterator
    
    Calling this method instructs the iterator to release any resources it holds, while still remaining able to deliver the remaining items in the sequence. This may require the iterator to calculate the rest of the sequence eagerly. The method is called by a client if it anticipates that it might not read the iterator to completion, but it cannot guarantee that SequenceIterator.close() will be called when no more items are needed.
    
    Specified by:
    
    discharge 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: LastPositionFinder
    
    Get the last position (that is, the number of items in the sequence). This method is non-destructive: it does not change the state of the iterator. The result is undefined if the next() method of the iterator has already returned null. This method must not be called unless the LastPositionFinder.supportsGetLength() has been called and has returned true.
    
    Specified by:
    
    getLength in interface LastPositionFinder
    
    Returns:
    
    the number of items in the sequence

Class ItemCheckingIterator

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Constructor Detail

ItemCheckingIterator

Method Detail

supportsHasNext

hasNext

next

close

discharge

supportsGetLength

getLength