EmptySequence

java.lang.Object
- net.sf.saxon.value.EmptySequence<T>

All Implemented Interfaces:

GroundedValue, Sequence
```
public final class EmptySequence<T extends Item>
extends Object
implements GroundedValue
```
An EmptySequence object represents a sequence containing no members.

Method Summary

Methods
Modifier and Type	Method and Description
`Item`	`asItem()` Return the value in the form of an Item
`boolean`	`effectiveBooleanValue()` Get the effective boolean value - always false
`boolean`	`equals(Object other)` Is this expression the same as another expression?
`int`	`getCardinality()` Determine the static cardinality
`static <T extends Item> EmptySequence<T>`	`getInstance()` Get the implicit instance of this class
`ItemType`	`getItemType(TypeHierarchy th)` Determine the item type
`int`	`getLength()` Get the length of the sequence
`String`	`getStringValue()` Get the string value of this sequence.
`CharSequence`	`getStringValueCS()` Get the string value of this sequence.
`int`	`hashCode()`
`Item`	`head()` Get the first item in the sequence.
`T`	`itemAt(int n)` Get the n'th item in the sequence (starting from 0).
`SequenceIterator<T>`	`iterate()` Return an iteration over the sequence
`GroundedValue`	`reduce()` Reduce the sequence to its simplest form.
`GroundedValue`	`subsequence(int min, int length)` Get a subsequence of the value
`String`	`toString()` Returns a string representation of the object.

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

- Method Detail
  - getInstance
```
public static <T extends Item> EmptySequence<T> getInstance()
```
    Get the implicit instance of this class
    
    Returns:
    the singular instances of this class: an empty sequence
  - getStringValue
```
public String getStringValue()
                      throws XPathException
```
    Description copied from interface: GroundedValue
    
    Get the string value of this sequence. The string value of an item is the result of applying the string() function. The string value of a sequence is the space-separated result of applying the string-join() function using a single space as the separator
    
    Specified by:
    
    getStringValue in interface GroundedValue
    
    Returns:
    the string value of the sequence.
    
    Throws:
    
    XPathException - if the sequence contains items that have no string value (for example, function items)
  - getStringValueCS
```
public CharSequence getStringValueCS()
                              throws XPathException
```
    Description copied from interface: GroundedValue
    
    Get the string value of this sequence. The string value of an item is the result of applying the string() function. The string value of a sequence is the space-separated result of applying the string-join() function using a single space as the separator
    
    Specified by:
    
    getStringValueCS in interface GroundedValue
    
    Returns:
    the string value of the sequence.
    
    Throws:
    
    XPathException - if the sequence contains items that have no string value (for example, function items)
  - head
```
public Item head()
          throws XPathException
```
    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<T> iterate()
```
    Return an iteration over the sequence
    
    Specified by:
    
    iterate in interface Sequence
    
    Returns:
    an iterator over all the items
  - asItem
```
public Item asItem()
```
    Return the value in the form of an Item
    
    Returns:
    the value in the form of an Item
  - getItemType
```
public ItemType getItemType(TypeHierarchy th)
```
    Determine the item type
    
    Parameters:
    th - the type hierarchy cache
  - getCardinality
```
public int getCardinality()
```
    Determine the static cardinality
  - getLength
```
public final int getLength()
```
    Get the length of the sequence
    
    Specified by:
    
    getLength in interface GroundedValue
    
    Returns:
    always 0 for an empty sequence
  - equals
```
public boolean equals(Object other)
```
    Is this expression the same as another expression?
    
    Overrides:
    
    equals in class Object
    
    Throws:
    
    ClassCastException - if the values are not comparable
  - hashCode
```
public int hashCode()
```
    Overrides:
    
    hashCode in class Object
  - effectiveBooleanValue
```
public boolean effectiveBooleanValue()
```
    Get the effective boolean value - always false
    
    Specified by:
    
    effectiveBooleanValue in interface GroundedValue
    
    Returns:
    the effective boolean value
  - itemAt
```
public T itemAt(int n)
```
    Get the n'th item in the sequence (starting from 0). This is defined for all Values, but its real benefits come for a sequence Value stored extensionally (or for a MemoClosure, once all the values have been read)
    
    Specified by:
    
    itemAt in interface GroundedValue
    
    Parameters:
    n - position of the required item, counting from zero.
    
    Returns:
    the n'th item in the sequence, where the first item in the sequence is numbered zero. If n is negative or >= the length of the sequence, returns null.
  - subsequence
```
public GroundedValue subsequence(int min,
                        int length)
```
    Get a subsequence of the value
    
    Specified by:
    
    subsequence in interface GroundedValue
    
    Parameters:
    min - the index of the first item to be included in the result, counting from zero. A negative value is taken as zero. If the value is beyond the end of the sequence, an empty sequence is returned
    length - the number of items to be included in the result. Specify Integer.MAX_VALUE to get the subsequence up to the end of the base sequence. If the value is negative, an empty sequence is returned. If the value goes off the end of the sequence, the result returns items up to the end of the sequence
    
    Returns:
    the required subsequence. If min is
  - toString
```
public String toString()
```
    Returns a string representation of the object.
    
    Overrides:
    
    toString in class Object
  - reduce
```
public GroundedValue reduce()
```
    Reduce the sequence to its simplest form. If the value is an empty sequence, the result will be EmptySequence.getInstance(). If the value is a single atomic value, the result will be an instance of AtomicValue. If the value is a single item of any other kind, the result will be an instance of SingletonItem. Otherwise, the result will typically be unchanged.
    
    Specified by:
    
    reduce in interface GroundedValue
    
    Returns:
    the simplified sequence

Class EmptySequence<T extends Item>

Method Summary

Methods inherited from class java.lang.Object

Method Detail

getInstance

getStringValue

getStringValueCS

head

iterate

asItem

getItemType

getCardinality

getLength

equals

hashCode

effectiveBooleanValue

itemAt

subsequence

toString

reduce