Class CalcStarTable<C>

java.lang.Object
uk.ac.starlink.table.AbstractStarTable
uk.ac.starlink.table.CalcStarTable<C>
Type Parameters:
C - type of object that is calculated from each row of the input table, and supplies values to the corresponding row of this table
All Implemented Interfaces:
Closeable, AutoCloseable, StarTable
public abstract class CalcStarTable<C> extends AbstractStarTable
StarTable implementation whose column values are derived from some single calculation on the column values of another table. The idea is that the cell values in a given row of an instance of this table are cheaply-obtained members of an object which is obtained by a potentially expensive calculation on the cell values of the corresponding row in the other table.

  • Constructor Details

    • CalcStarTable

      public CalcStarTable(StarTable base, CalcStarTable.Col<C,?>[] columns)
      Constructor.
      Parameters:
      base - input table
      columns - array defining the columns of this table

  • Method Details

    • createCalculation

      public abstract C createCalculation(RowData baseRow) throws IOException
      Creates the calculation object for the current row of the input table.
      Parameters:
      baseRow - row from base table
      Returns:
      calculation object corresponding to baseRow
      Throws:
      IOException

    • createCalculation

      public abstract C createCalculation(long irow) throws IOException
      Creates the calculation object for the given row of the input table. Only works for random-access tables.
      Parameters:
      irow - row index for which calculation is required
      Returns:
      calculation object for input table row irow
      Throws:
      IOException

    • getBaseTable

      public StarTable getBaseTable()
      Returns the input table on which this table is based.
      Returns:
      base table

    • getColumnInfo

      public ColumnInfo getColumnInfo(int icol)
      Description copied from interface: StarTable
      Returns the object describing the data in a given column.
      Specified by:
      getColumnInfo in interface StarTable
      Specified by:
      getColumnInfo in class AbstractStarTable
      Parameters:
      icol - the column for which header information is required
      Returns:
      a ValueInfo object for column icol

    • getColumnCount

      public int getColumnCount()
      Description copied from interface: StarTable
      Returns the number of columns in this table.
      Specified by:
      getColumnCount in interface StarTable
      Specified by:
      getColumnCount in class AbstractStarTable
      Returns:
      the number of columns

    • getRowCount

      public long getRowCount()
      Description copied from interface: StarTable
      Returns the number of rows in this table, if known. If the number of rows cannot be (easily) determined, a value of -1 will be returned.
      Specified by:
      getRowCount in interface StarTable
      Specified by:
      getRowCount in class AbstractStarTable
      Returns:
      the number of rows, or -1

    • isRandom

      public boolean isRandom()
      Description copied from class: AbstractStarTable
      The AbstractStarTable implementation of this method returns false.
      Specified by:
      isRandom in interface StarTable
      Overrides:
      isRandom in class AbstractStarTable
      Returns:
      true if table random access methods are available

    • getRowSequence

      public RowSequence getRowSequence() throws IOException
      Description copied from interface: StarTable
      Returns an object which can iterate over all the rows in the table sequentially. Each such returned object is safe for use within a single thread, but not in general from multiple threads concurrently.
      Specified by:
      getRowSequence in interface StarTable
      Specified by:
      getRowSequence in class AbstractStarTable
      Returns:
      new RowSequence
      Throws:
      IOException - if there is an error providing access

    • getRowSplittable

      public RowSplittable getRowSplittable() throws IOException
      Description copied from class: AbstractStarTable
      Returns a default splittable which relies on table random access if available, or otherwise provides only sequential access (no splits).

      It is often possible to provide a better implementation than this.

      Specified by:
      getRowSplittable in interface StarTable
      Overrides:
      getRowSplittable in class AbstractStarTable
      Returns:
      Tables.getDefaultRowSplittable(this)
      Throws:
      IOException
      See Also:

    • getRowAccess

      public RowAccess getRowAccess() throws IOException
      Description copied from interface: StarTable
      Returns an object which can provide random access to this table's data, if random access is implemented. Each such returned object is safe for use within a single thread, but not in general from multiple threads concurrently.
      Specified by:
      getRowAccess in interface StarTable
      Overrides:
      getRowAccess in class AbstractStarTable
      Returns:
      new RowAccess
      Throws:
      IOException - if there is an error setting up access

    • getRow

      public Object[] getRow(long irow) throws IOException
      Description copied from class: AbstractStarTable
      The AbstractStarTable implementation of this method constructs a row by repeated invocation of AbstractStarTable.getCell(long, int).
      Specified by:
      getRow in interface StarTable
      Overrides:
      getRow in class AbstractStarTable
      Parameters:
      irow - the index of the row to retrieve
      Returns:
      an array of the objects in each cell in row irow
      Throws:
      IOException - if there is an error reading the data

    • getCell

      public Object getCell(long irow, int icol) throws IOException
      Description copied from class: AbstractStarTable
      The AbstractStarTable implementation of this method throws an UnsupportedOperationException, since unless otherwise provided there is no random access.
      Specified by:
      getCell in interface StarTable
      Overrides:
      getCell in class AbstractStarTable
      Parameters:
      irow - the index of the cell's row
      icol - the index of the cell's column
      Returns:
      the contents of this cell
      Throws:
      IOException - if there is an error reading the data

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