uk.ac.starlink.table
Interface RowSequence

All Known Implementing Classes:
IteratorRowSequence, RandomRowSequence, ReaderRowSequence, WrapperRowSequence

public interface RowSequence

Provides sequential access to the data in a table. The data is a sequence of rows which may be processed from the first to the last. This object has a current row index which starts off at -1, that is before the first row; the next method must be invoked before the first row can be accessed.

A RowSequence cannot in general be expected to be used safely from multiple threads.


Method Summary
 void advance(long nrows)
          Moves the current row forward by offset rows.
 Object getCell(int icol)
          Returns the contents of a cell in the current row.
 Object[] getRow()
          Returns the contents of the current table row, as an array with the same number of elements as there are columns in this table.
 long getRowIndex()
          Returns the index of the current row.
 boolean hasNext()
          Indicates whether this table contains any more rows after the current one.
 void next()
          Advances the current row by 1.
 

Method Detail

next

public void next()
          throws IOException
Advances the current row by 1. Since the initial value of the current row is -1, next must be called before current row data as accessed by the getCell(int) or getRow() methods are invoked.

Throws:
IOException - if there is some error in the positioning
IllegalStateException - if there are no more rows (hasNext() returns false)

hasNext

public boolean hasNext()
Indicates whether this table contains any more rows after the current one.

Returns:
true iff another row exists

advance

public void advance(long nrows)
             throws IOException
Moves the current row forward by offset rows.

Parameters:
nrows - the number of rows to advance the current row by.
Throws:
IllegalArgumentException - if nrows<0
IOException - if an attempt to advance beyond the end of the table is made, or if there is some other read error

getCell

public Object getCell(int icol)
               throws IOException
Returns the contents of a cell in the current row. The class of the returned object should be the same as, or a subclass of, the class returned by getColumnInfo(icol).getContentClass().

Returns:
the contents of cell icol in the current row
Throws:
IOException - if there is an error reading the data
IllegalStateException - if there is no current row (before the start of the table)

getRow

public Object[] getRow()
                throws IOException
Returns the contents of the current table row, as an array with the same number of elements as there are columns in this table.

Returns:
an array of the objects in each cell in row irow
Throws:
IOException - if there is an error reading the data
IllegalStateException - if there is no current row (before the start of the table)

getRowIndex

public long getRowIndex()
Returns the index of the current row. This starts off at -1 before the first invocation of next.

Returns:
the index of the current row

Copyright © 2004 CLRC: Central Laboratory of the Research Councils. All rights reserved.