Class EmptyRowSequence
- java.lang.Object
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- uk.ac.starlink.table.EmptyRowSequence
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- All Implemented Interfaces:
java.io.Closeable
,java.lang.AutoCloseable
,RowAccess
,RowData
,RowSequence
,RowSplittable
,uk.ac.starlink.util.Sequence
,uk.ac.starlink.util.Splittable<RowSplittable>
public class EmptyRowSequence extends java.lang.Object implements RowSplittable, RowAccess
Implementation of both RowSequence and RowAccess which has no rows. Singleton class.- Since:
- 28 Oct 2004
- Author:
- Mark Taylor (Starlink)
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Method Summary
All Methods Static Methods Instance Methods Concrete Methods Modifier and Type Method Description void
close()
Does nothing.java.lang.Object
getCell(int icol)
Always throws IllegalStateException.static EmptyRowSequence
getInstance()
Returns singleton instance of this class.java.lang.Object[]
getRow()
Always throws IllegalStateException.boolean
next()
Always returns false.java.util.function.LongSupplier
rowIndex()
Returns a supplier for the index of the row currently being processed, if possible.void
setRowIndex(long irow)
Sets the row index to which subsequent data accesses will refer.RowSplittable
split()
long
splittableSize()
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Method Detail
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next
public boolean next()
Always returns false.- Specified by:
next
in interfaceRowSequence
- Specified by:
next
in interfaceuk.ac.starlink.util.Sequence
- Returns:
- true iff this sequence has been advanced to the next row
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setRowIndex
public void setRowIndex(long irow)
Description copied from interface:RowAccess
Sets the row index to which subsequent data accesses will refer.This method must be called before the first invocation of
RowAccess.getCell(int)
/RowAccess.getRow()
, otherwise behaviour is undefined (but implementations will likely throw an unchecked exception on subsequent getCell/getRow calls). The effect of setting the value to an out of range value is undefined; it may throw an exception here, or during subsequent calls, or behave otherwise.- Specified by:
setRowIndex
in interfaceRowAccess
- Parameters:
irow
- row index
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rowIndex
public java.util.function.LongSupplier rowIndex()
Description copied from interface:RowSplittable
Returns a supplier for the index of the row currently being processed, if possible. The row index is a global value; when accessing the first row of a top-level RowSplittable, the value returned by this supplier should be the first index in the table. But for objects resulting from splitting a top-level instance into sub-instances, the return value should reflect the index in the original sequence of rows; each index should be returned from only one of the splittables resulting from splitting a top-level instance.Typically, the row index will start at 0 and increment for each row, but the numbering may be different depending on the requirements of the implementation or usage.
Before the
RowSequence.next()
method has been called, the return value will be one less than the first row index. AfterRowSequence.next
has returned false, the value is undefined.Depending on the implementation, it may not be possible to determine the row index (for instance if the sequence is split into sub-splittables of unknown size). In such cases, this method returns null. The null-ness of the return value must be the same for all instances of the splittable hierarchy for a given sequence, so don't return a non-null value for the first splittable and then null values for some or all of its children.
- Specified by:
rowIndex
in interfaceRowSplittable
- Returns:
- supplier for the globally-referenced row index value of the current row of this sequence, or null
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split
public RowSplittable split()
- Specified by:
split
in interfaceuk.ac.starlink.util.Splittable<RowSplittable>
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splittableSize
public long splittableSize()
- Specified by:
splittableSize
in interfaceuk.ac.starlink.util.Splittable<RowSplittable>
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getCell
public java.lang.Object getCell(int icol)
Always throws IllegalStateException.
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getRow
public java.lang.Object[] getRow()
Always throws IllegalStateException.
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close
public void close()
Does nothing.- Specified by:
close
in interfacejava.lang.AutoCloseable
- Specified by:
close
in interfacejava.io.Closeable
- Specified by:
close
in interfaceRowAccess
- Specified by:
close
in interfaceRowSequence
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getInstance
public static EmptyRowSequence getInstance()
Returns singleton instance of this class.- Returns:
- instance
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