uk.ac.starlink.table
Class ReaderRowSequence

java.lang.Object
  |
  +--uk.ac.starlink.table.ReaderRowSequence
All Implemented Interfaces:
RowSequence

public abstract class ReaderRowSequence
extends Object
implements RowSequence

Partial implementation of RowSequence suitable for subclassing by classes which can read a row at a time and don't know when the row stream will come to an end. Concrete subclasses have to implement the readRow() method.


Constructor Summary
ReaderRowSequence()
           
 
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.
protected abstract  Object[] readRow()
          Acquires the next row of objects from the input stream.
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

ReaderRowSequence

public ReaderRowSequence()
                  throws IOException
Method Detail

readRow

protected abstract Object[] readRow()
                             throws IOException
Acquires the next row of objects from the input stream. When there are no more rows to read this method must return null; note it should not throw an EOFException. Otherwise it must return an array of objects representing the row content for the next row.

Returns:
the next row, or null if there are no more
Throws:
IOException - if there is trouble reading the data

next

public void next()
          throws IOException
Description copied from interface: RowSequence
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 RowSequence.getCell(int) or RowSequence.getRow() methods are invoked.

Specified by:
next in interface RowSequence
Throws:
IOException - if there is some error in the positioning

hasNext

public boolean hasNext()
Description copied from interface: RowSequence
Indicates whether this table contains any more rows after the current one.

Specified by:
hasNext in interface RowSequence
Returns:
true iff another row exists

advance

public void advance(long nrows)
             throws IOException
Description copied from interface: RowSequence
Moves the current row forward by offset rows.

Specified by:
advance in interface RowSequence
Parameters:
nrows - the number of rows to advance the current row by.
Throws:
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)
Description copied from interface: RowSequence
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().

Specified by:
getCell in interface RowSequence
Returns:
the contents of cell icol in the current row

getRow

public Object[] getRow()
Description copied from interface: RowSequence
Returns the contents of the current table row, as an array with the same number of elements as there are columns in this table.

Specified by:
getRow in interface RowSequence
Returns:
an array of the objects in each cell in row irow

getRowIndex

public long getRowIndex()
Description copied from interface: RowSequence
Returns the index of the current row. This starts off at -1 before the first invocation of next.

Specified by:
getRowIndex in interface RowSequence
Returns:
the index of the current row

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