Interface TupleCursor
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- All Known Subinterfaces:
TupleIterator
- All Known Implementing Classes:
AbstractTupleCursor
,AbstractTupleIterator
,AbstractTupleList.AbstractTupleListIterator
public interface TupleCursor
Cheap interface for iterating through the contents of aTupleList
.Stops short of the full
Iterator
interface. If you want that, seeTupleIterator
.- Author:
- Julian Hyde
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Method Summary
All Methods Instance Methods Abstract Methods Modifier and Type Method Description List<Member>
current()
Returns the tuple that this cursor is positioned on.void
currentToArray(Member[] members, int offset)
Writes the member(s) of the next tuple to a given offset in an array.boolean
forward()
Moves the iterator forward one position.int
getArity()
Returns the number of members in each tuple.Member
member(int column)
void
setContext(Evaluator evaluator)
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Method Detail
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setContext
void setContext(Evaluator evaluator)
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forward
boolean forward()
Moves the iterator forward one position.Returns false only when end of data has been reached.
Similar to calling the
Iterator
methodsIterator.hasNext()
followed byIterator.next()
but does not construct an object, and is therefore cheaper.If you want to use an Iterator, see
TupleIterator
.- Returns:
- Whether was able to move forward a position
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current
List<Member> current()
Returns the tuple that this cursor is positioned on.This method never returns null, and may safely be called multiple times (or not all) for each position in the iteration.
Invalid to call this method when the cursor is has not been positioned, for example, if
forward()
has not been called or if the most recent call toforward
returnedfalse
.- Returns:
- Current tuple
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getArity
int getArity()
Returns the number of members in each tuple.- Returns:
- The number of members in each tuple
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member
Member member(int column)
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currentToArray
void currentToArray(Member[] members, int offset)
Writes the member(s) of the next tuple to a given offset in an array.This method saves the overhead of a memory allocation when the resulting tuple will be written immediately to an array. The effect of
currentToArray(members, 0)
is the same as callingcurrent().toArray(members)
.Before calling this method, you must position the iterator at a valid position. Typically you would call hasNext followed by next; or forward.
- Parameters:
members
- Membersoffset
- Offset in the array to write to
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