MemoSequence

java.lang.Object
- net.sf.saxon.om.MemoSequence

All Implemented Interfaces:

Sequence
```
public class MemoSequence
extends java.lang.Object
implements Sequence
```
A Sequence implementation that represents a lazy evaluation of a supplied iterator. Items are read from the base iterator only when they are first required, and are then remembered within the local storage of the MemoSequence, which eventually (if the sequence is read to the end) contains the entire value.

Nested Class Summary

Nested Classes
Modifier and Type	Class	Description
`static class`	`MemoSequence.ProgressiveIterator`	A ProgressiveIterator starts by reading any items already held in the reservoir; when the reservoir is exhausted, it reads further items from the inputIterator, copying them into the reservoir as they are read.

Constructor Summary

Constructors
Constructor Description

MemoSequence(SequenceIterator iterator)

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`Item`	`head()`	Get the first item in the sequence.
`Item`	`itemAt(int n)`	Get the Nth item in the sequence (0-based), reading new items into the internal reservoir if necessary
`SequenceIterator`	`iterate()`	Get a `SequenceIterator` over all the items in the sequence

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

Methods inherited from interface net.sf.saxon.om.Sequence
makeRepeatable, materialize

- Constructor Detail
  - MemoSequence
```
public MemoSequence(SequenceIterator iterator)
```
- Method Detail
  - head
```
public Item head()
          throws XPathException
```
    Description copied from interface: Sequence
    
    Get the first item in the sequence.
    
    Specified by:
    
    head in interface Sequence
    
    Returns:
    
    the first item in the sequence if there is one, or null if the sequence is empty
    
    Throws:
    
    XPathException - in the situation where the sequence is evaluated lazily, and evaluation of the first item causes a dynamic error.
  - iterate
```
public SequenceIterator iterate()
```
    Description copied from interface: Sequence
    
    Get a SequenceIterator over all the items in the sequence
    
    Specified by:
    
    iterate in interface Sequence
    
    Returns:
    
    an iterator (specifically, a Saxon SequenceIterator, which is not a Iterator) over all the items
  - itemAt
```
public Item itemAt(int n)
            throws XPathException
```
    Get the Nth item in the sequence (0-based), reading new items into the internal reservoir if necessary
    
    Parameters:
    
    n - the index of the required item
    
    Returns:
    
    the Nth item if it exists, or null otherwise
    
    Throws:
    
    XPathException - if the input sequence cannot be read