Package net.sf.saxon.om
Class ZeroOrOne<T extends Item>
- java.lang.Object
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- net.sf.saxon.om.ZeroOrOne<T>
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- All Implemented Interfaces:
GroundedValue,Sequence
- Direct Known Subclasses:
One
public class ZeroOrOne<T extends Item> extends java.lang.Object implements GroundedValue
A value that is a sequence containing zero or one items.
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Method Summary
All Methods Static Methods Instance Methods Concrete Methods Modifier and Type Method Description booleaneffectiveBooleanValue()Get the effective boolean valuestatic <T extends Item>
ZeroOrOne<T>empty()Return the instance of ZeroOrOne that represents the empty sequenceintgetLength()Get the length of the sequencejava.lang.StringgetStringValue()Convert the value to a string, using the serialization rules.java.lang.CharSequencegetStringValueCS()Get the string value of this sequence.Thead()Get the first item in the sequence.TitemAt(int n)Get the n'th item in the sequence (starting from 0).ConstrainedIterator<T>iterate()Return an iterator over this value.GroundedValuereduce()Reduce the sequence to its simplest form.GroundedValuesubsequence(int start, int length)Get a subsequence of the valuejava.lang.StringtoString()Returns a string representation of the object (used only for diagnostics).-
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait
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Methods inherited from interface net.sf.saxon.om.GroundedValue
asIterable, concatenate, containsNode, materialize, toShortString
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Methods inherited from interface net.sf.saxon.om.Sequence
makeRepeatable
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Constructor Detail
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ZeroOrOne
public ZeroOrOne(T item)
Create a sequence containing zero or one items- Parameters:
item- The item to be contained in the sequence, or null if the sequence is to be empty
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Method Detail
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empty
public static <T extends Item> ZeroOrOne<T> empty()
Return the instance of ZeroOrOne that represents the empty sequence- Returns:
- a representation of the empty sequence that satisfies the type ZeroOrOne
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getStringValueCS
public java.lang.CharSequence getStringValueCS()
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 an empty sequence is the zero-length string.- Specified by:
getStringValueCSin interfaceGroundedValue- Returns:
- the string value of the sequence.
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getStringValue
public java.lang.String getStringValue()
Convert the value to a string, using the serialization rules. For atomic values this is the same as a cast; for sequence values it gives a space-separated list. For QNames and NOTATIONS, or lists containing them, it fails.- Specified by:
getStringValuein interfaceGroundedValue- Returns:
- the string value of the sequence.
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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
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getLength
public int getLength()
Get the length of the sequence- Specified by:
getLengthin interfaceGroundedValue- Returns:
- the number of items in the sequence. Note that for a single item, including a map or array, the result is always 1 (one).
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itemAt
public T itemAt(int n)
Get the n'th item in the sequence (starting from 0). This is defined for all SequenceValues, but its real benefits come for a SequenceValue stored extensionally (or for a MemoClosure, once all the values have been read)- Specified by:
itemAtin interfaceGroundedValue- Parameters:
n- the index of the required item, with 0 representing the first item in the sequence- Returns:
- the n'th item if it exists, or null otherwise
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subsequence
public GroundedValue subsequence(int start, int length)
Get a subsequence of the value- Specified by:
subsequencein interfaceGroundedValue- Parameters:
start- 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
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iterate
public ConstrainedIterator<T> iterate()
Return an iterator over this value.- 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.
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effectiveBooleanValue
public boolean effectiveBooleanValue() throws XPathExceptionGet the effective boolean value- Specified by:
effectiveBooleanValuein interfaceGroundedValue- Returns:
- the effective boolean value
- Throws:
XPathException- if the sequence has no effective boolean value (for example a sequence of two integers)
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toString
public java.lang.String toString()
Returns a string representation of the object (used only for diagnostics).- Overrides:
toStringin classjava.lang.Object- Returns:
- a string representation of the object.
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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
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