Package uk.ac.starlink.table
Class EmptyStarTable
- java.lang.Object
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- uk.ac.starlink.table.WrapperStarTable
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- uk.ac.starlink.table.EmptyStarTable
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- All Implemented Interfaces:
java.io.Closeable
,java.lang.AutoCloseable
,StarTable
public class EmptyStarTable extends WrapperStarTable
A wrapper table which has the same metadata as its base table, but no rows.- Since:
- 5 Aug 2004
- Author:
- Mark Taylor (Starlink)
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Field Summary
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Fields inherited from class uk.ac.starlink.table.WrapperStarTable
baseTable
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Constructor Summary
Constructors Constructor Description EmptyStarTable()
Creates a new empty table with no columns, no rows and no parameters.EmptyStarTable(StarTable baseTable)
Creates a new empty table with metadata taken from an existing one.
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description java.lang.Object
getCell(long lrow, int icol)
Returns the contents of a given table cell.java.lang.Object[]
getRow(long lrow)
Returns the contents of a given table row.RowAccess
getRowAccess()
Returns an object which can provide random access to this table's data, if random access is implemented.long
getRowCount()
Returns the number of rows in this table, if known.RowSequence
getRowSequence()
Returns an object which can iterate over all the rows in the table sequentially.RowSplittable
getRowSplittable()
Returns an object which can iterate over all the rows in the table, but which may also be requested to split recursively for potentially parallel processing.boolean
isRandom()
Indicates whether random access is provided by this table.-
Methods inherited from class uk.ac.starlink.table.WrapperStarTable
checkedLongToInt, close, getBaseTable, getColumnAuxDataInfos, getColumnCount, getColumnInfo, getName, getParameterByName, getParameters, getURL, setName, setParameter, setURL, toString
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Constructor Detail
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EmptyStarTable
public EmptyStarTable(StarTable baseTable)
Creates a new empty table with metadata taken from an existing one.- Parameters:
baseTable
- base table
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EmptyStarTable
public EmptyStarTable()
Creates a new empty table with no columns, no rows and no parameters.
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Method Detail
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isRandom
public boolean isRandom()
Description copied from interface:StarTable
Indicates whether random access is provided by this table. Only if the result is true may theStarTable.getRowAccess()
,StarTable.getRow(long)
andStarTable.getCell(long, int)
methods be used.- Specified by:
isRandom
in interfaceStarTable
- Overrides:
isRandom
in classWrapperStarTable
- Returns:
- true if table random access methods are available
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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 interfaceStarTable
- Overrides:
getRowCount
in classWrapperStarTable
- Returns:
- the number of rows, or -1
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getCell
public java.lang.Object getCell(long lrow, int icol)
Description copied from interface:StarTable
Returns the contents of a given table cell. The class of the returned object should be the same as, or a subclass of, the class returned by getColumnInfo(icol).getContentClass().This method is safe for concurrent use from multiple threads, but in general it is recommended to use a
RowAccess
instead.- Specified by:
getCell
in interfaceStarTable
- Overrides:
getCell
in classWrapperStarTable
- Parameters:
lrow
- the index of the cell's rowicol
- the index of the cell's column- Returns:
- the contents of this cell
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getRow
public java.lang.Object[] getRow(long lrow)
Description copied from interface:StarTable
Returns the contents of a given table row. The returned value is equivalent to an array formed of all the objects returned by getCell(irow,icol) for all the columns icol in sequence.This method is safe for concurrent use from multiple threads, but in general it is recommended to use a
RowAccess
instead.- Specified by:
getRow
in interfaceStarTable
- Overrides:
getRow
in classWrapperStarTable
- Parameters:
lrow
- the index of the row to retrieve- Returns:
- an array of the objects in each cell in row irow
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getRowSequence
public RowSequence getRowSequence()
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 interfaceStarTable
- Overrides:
getRowSequence
in classWrapperStarTable
- Returns:
- new RowSequence
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getRowAccess
public RowAccess getRowAccess()
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 interfaceStarTable
- Overrides:
getRowAccess
in classWrapperStarTable
- Returns:
- new RowAccess
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getRowSplittable
public RowSplittable getRowSplittable()
Description copied from interface:StarTable
Returns an object which can iterate over all the rows in the table, but which may also be requested to split recursively for potentially parallel processing.The return value must be non-null, and may provide splitting arrangements specially appropriate for the implementation. If this table 'wraps' an upstream table, it is usually best to base the implementation on calls to the the upstream
getRowSplittable
method, so that upstream policy about how to divide up the table is respected. However, implementations without special requirements may returnTables.getDefaultRowSplittable
(this)
.- Specified by:
getRowSplittable
in interfaceStarTable
- Overrides:
getRowSplittable
in classWrapperStarTable
- Returns:
- new RowSplittable
- See Also:
RowRunner
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