Package net.sf.saxon.value

Class EmptySequence<T extends Item>

  • 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 Detail

      • a

        public java.util.Collections a

    • 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: 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.

      • getStringValueCS

        public java.lang.CharSequence getStringValueCS()
        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.

      • head

        public T head()
        Get the first item in the sequence.
        Specified by:
        head in interface GroundedValue
        Specified by:
        head in interface Sequence
        Returns:
        the first item in the sequence if there is one, or null if the sequence is empty

      • 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:
        getLength in interface GroundedValue
        Returns:
        always 0 for an empty sequence

      • equals

        public boolean equals​(java.lang.Object other)
        Is this expression the same as another expression?
        Overrides:
        equals in class java.lang.Object
        Throws:
        java.lang.ClassCastException - if the values are not comparable

      • hashCode

        public int hashCode()
        Overrides:
        hashCode in class java.lang.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 java.lang.String toString()
        Returns a string representation of the object.
        Overrides:
        toString in class java.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:
        reduce in interface GroundedValue
        Returns:
        the simplified sequence