Package net.sf.saxon.value
Class EmptySequence<T extends Item>
- java.lang.Object
-
- net.sf.saxon.value.EmptySequence<T>
-
- All Implemented Interfaces:
GroundedValue,Sequence
public final class EmptySequence<T extends Item> extends java.lang.Object implements GroundedValue
An EmptySequence object represents a sequence containing no members.
-
-
Field Summary
Fields Modifier and Type Field Description java.util.Collectionsa
-
Method Summary
All Methods Static Methods Instance Methods Concrete Methods Modifier and Type Method Description ItemasItem()Return the value in the form of an ItembooleaneffectiveBooleanValue()Get the effective boolean value - always falsebooleanequals(java.lang.Object other)Is this expression the same as another expression?static <T extends Item>
EmptySequence<T>getInstance()Get the implicit instance of this classintgetLength()Get the length of the sequencejava.lang.StringgetStringValue()Get the string value of this sequence.java.lang.CharSequencegetStringValueCS()Get the string value of this sequence.inthashCode()Thead()Get the first item in the sequence.TitemAt(int n)Get the n'th item in the sequence (starting from 0).UnfailingIteratoriterate()Return an iteration over the sequenceGroundedValuereduce()Reduce the sequence to its simplest form.GroundedValuesubsequence(int min, int length)Get a subsequence of the valuejava.lang.StringtoString()Returns a string representation of the object.-
Methods inherited from class java.lang.Object
clone, finalize, getClass, notify, notifyAll, wait, wait, wait
-
Methods inherited from interface net.sf.saxon.om.GroundedValue
asIterable, concatenate, containsNode, materialize, toShortString
-
Methods inherited from interface net.sf.saxon.om.Sequence
makeRepeatable
-
-
-
-
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 java.lang.String getStringValue()
Description copied from interface:GroundedValueGet 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:
getStringValuein interfaceGroundedValue- Returns:
- the string value of the sequence.
-
getStringValueCS
public java.lang.CharSequence getStringValueCS()
Description copied from interface:GroundedValueGet 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:
getStringValueCSin interfaceGroundedValue- Returns:
- the string value of the sequence.
-
head
public T head()
Get the first item in the sequence.- Specified by:
headin interfaceGroundedValue- Specified by:
headin interfaceSequence- Returns:
- the first item in the sequence if there is one, or null if the sequence is empty
-
iterate
public UnfailingIterator iterate()
Return an iteration over the sequence- Specified by:
iteratein interfaceGroundedValue- Specified by:
iteratein interfaceSequence- Returns:
- an iterator (meaning a Saxon
SequenceIteratorrather than a JavaIterator) over all the items in this Sequence.
-
asItem
public Item asItem()
Return the value in the form of an Item- Returns:
- the value in the form of an Item
-
getLength
public final int getLength()
Get the length of the sequence- Specified by:
getLengthin interfaceGroundedValue- Returns:
- always 0 for an empty sequence
-
equals
public boolean equals(java.lang.Object other)
Is this expression the same as another expression?- Overrides:
equalsin classjava.lang.Object- Throws:
java.lang.ClassCastException- if the values are not comparable
-
hashCode
public int hashCode()
- Overrides:
hashCodein classjava.lang.Object
-
effectiveBooleanValue
public boolean effectiveBooleanValue()
Get the effective boolean value - always false- Specified by:
effectiveBooleanValuein interfaceGroundedValue- 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:
itemAtin interfaceGroundedValue- 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:
subsequencein interfaceGroundedValue- 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 returnedlength- 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 java.lang.String toString()
Returns a string representation of the object.- Overrides:
toStringin classjava.lang.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:
reducein interfaceGroundedValue- Returns:
- the simplified sequence
-
-