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## net.sf.saxon.value
Class ShareableSequence

    java.lang.Object
      net.sf.saxon.value.Value
          net.sf.saxon.value.ShareableSequence

All Implemented Interfaces:
  Expression, java.io.Serializable, ValueRepresentation

public final class ShareableSequence
extends Value

A sequence value implemented extensionally using an extensible List whose leading part can be shared with other sequence values. The list can be appended to by other users (at most one other user!), but the items within the range used by this sequence value cannot be modified.

See Also:
  Serialized Form

Field Summary

Fields inherited from class net.sf.saxon.value.Value
`EMPTY_CLASS_ARRAY`

Fields inherited from interface net.sf.saxon.expr.Expression
`EVALUATE_METHOD, ITERATE_METHOD, PROCESS_METHOD`

Fields inherited from interface net.sf.saxon.om.ValueRepresentation
`EMPTY_VALUE_ARRAY`

Constructor Summary
`ShareableSequence(java.util.List list)` Construct an sequence from an array of items.

Method Summary
`boolean` | `effectiveBooleanValue(XPathContext context)` Get the effective boolean value
`int` | `getCardinality()` Determine the cardinality
`int` | `getImplementationMethod()` An implementation of Expression must provide at least one of the methods evaluateItem(), iterate(), or process().
`ItemType` | `getItemType(TypeHierarchy th)` Get the (lowest common) item type
`int` | `getLength()` Get the number of items in the sequence
`java.util.List` | `getList()` Get the underlying list
`boolean` | `isShareable()` Determine whether another value can share this list.
`Item` | `itemAt(int n)` Get the n'th item in the sequence (starting with 0 as the first item)
`SequenceIterator` | `iterate(XPathContext context)` Return an iterator over this sequence.
`Value` | `reduce()` Reduce a value to its simplest form.
`Value` | `simplify()` Simplify this value

Methods inherited from class net.sf.saxon.value.Value
`asItem, asIterator, asValue, checkPermittedContents, collapseWhitespace, convert, convertJavaObjectToXPath, convertToJava, display, equals, evaluateAsString, evaluateItem, getDependencies, getIterator, getParentExpression, getSpecialProperties, getStringValue, hashCode, iterateSubExpressions, makeQNameValue, normalizeWhitespace, optimize, process, promote, schemaEquals, simplify, stringToNumber, toString, trimWhitespace, typeCheck`

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

Constructor Detail

### ShareableSequence

    public ShareableSequence(java.util.List list)

  Construct an sequence from an array of items. Note, the list of items is used as is, which means the caller must not subsequently change its contents; however it is permitted to subsequently append items to the list (indeed, that is the raison d'etre of this class)

Parameters:
  `list` - the list of items to be included in the sequence

Method Detail

### isShareable

    public boolean isShareable()

  Determine whether another value can share this list. This is true provided the list has not already been extended by another value.

### getList

    public java.util.List getList()

  Get the underlying list

### getImplementationMethod

    public int getImplementationMethod()

  An implementation of Expression must provide at least one of the methods evaluateItem(), iterate(), or process(). This method indicates which of these methods is preferred.

### simplify

    public Value simplify()

  Simplify this value

### reduce

    public Value reduce()

  Reduce a value to its simplest form. If the value is a closure or some other form of deferred value such as a FunctionCallPackage, then it is reduced to a SequenceExtent. If it is a SequenceExtent containing a single item, then it is reduced to that item. One consequence that is exploited by class FilterExpression is that if the value is a singleton numeric value, then the result will be an instance of NumericValue

  Overrides:
    `reduce` in class `Value`

### getLength

    public int getLength()

  Get the number of items in the sequence

  Overrides:
    `getLength` in class `Value`
  Returns:
    the number of items in the sequence

### getCardinality

    public int getCardinality()

  Determine the cardinality

  Specified by:
    `getCardinality` in interface `Expression`
  Overrides:
    `getCardinality` in class `Value`
  Returns:
    the cardinality of the sequence, using the constants defined in net.sf.saxon.value.Cardinality
  See Also:
    `Cardinality`

### getItemType

    public ItemType getItemType(TypeHierarchy th)

  Get the (lowest common) item type

  Specified by:
    `getItemType` in interface `Expression`
  Overrides:
    `getItemType` in class `Value`
  Parameters:
    `th` -
  Returns:
    integer identifying an item type to which all the items in this sequence conform

### itemAt

    public Item itemAt(int n)

  Get the n'th item in the sequence (starting with 0 as the first item)

  Overrides:
    `itemAt` in class `Value`
  Parameters:
    `n` - the position of the required item
  Returns:
    the n'th item in the sequence

### iterate

    public SequenceIterator iterate(XPathContext context)

  Return an iterator over this sequence.

  Parameters:
    `context` - dynamic evaluation context; not used in this implementation of the method
  Returns:
    the required SequenceIterator, positioned at the start of the sequence

### effectiveBooleanValue

    public boolean effectiveBooleanValue(XPathContext context)
                                  throws XPathException

  Get the effective boolean value

  Specified by:
    `effectiveBooleanValue` in interface `Expression`
  Overrides:
    `effectiveBooleanValue` in class `Value`
  Parameters:
    `context` - The context in which the expression is to be evaluated
  Returns:
    the effective boolean value
  Throws:
    `XPathException` - if any dynamic error occurs evaluating the expression

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