Class WrapperStarTable
- java.lang.Object
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- uk.ac.starlink.table.WrapperStarTable
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- All Implemented Interfaces:
java.io.Closeable
,java.lang.AutoCloseable
,StarTable
- Direct Known Subclasses:
ColumnPermutedStarTable
,ColumnStoreStarTable
,ConcatStarTable
,EmptyStarTable
,ExplodedStarTable
,MetaCopyStarTable
,ProgressBarStarTable
,ProgressLineStarTable
,RowPermutedStarTable
,RowSubsetStarTable
,SelectorStarTable
public class WrapperStarTable extends java.lang.Object implements StarTable
StarTable which wraps another StarTable. This class acts as a wrapper around an existing 'base' StarTable object; almost all its methods are implemented by forwarding to the corresponding methods of that base table. The exception is thegetURL()
method which returns null as an indication that the actual table is not a persistent one (though it may be based on, and even identical to, a persistent one).This class is provided so that it can be extended by subclasses which modify the view of the base table in useful ways.
Subclasses should take care to ensure that all the data access methods are overridden in a consistent way:
getCell(long, int)
,getRow(long)
,getRowSequence()
,getRowAccess()
andgetRowSplittable()
.- Author:
- Mark Taylor (Starlink)
- See Also:
WrapperRowSequence
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Constructor Summary
Constructors Constructor Description WrapperStarTable(StarTable baseTable)
Constructs a new WrapperStarTable from a given base table.
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Method Summary
All Methods Static Methods Instance Methods Concrete Methods Modifier and Type Method Description static int
checkedLongToInt(long lval)
Convenience method to get an int value from a long.void
close()
Relinquishes any resources associated with this table.StarTable
getBaseTable()
Returns the base table underlying this wrapper table.java.lang.Object
getCell(long irow, int icol)
Returns the contents of a given table cell.java.util.List<ValueInfo>
getColumnAuxDataInfos()
Returns an ordered list of ValueInfo objects representing the auxiliary metadata returned by getColumnInfo(int).getAuxData() calls.int
getColumnCount()
Returns the number of columns in this table.ColumnInfo
getColumnInfo(int icol)
Returns the object describing the data in a given column.java.lang.String
getName()
Returns the name of this table, if it has one.DescribedValue
getParameterByName(java.lang.String parname)
Returns a parameter (table-wide metadata item) of this table located by its name.java.util.List<DescribedValue>
getParameters()
Returns a list of table parameters, that is metadata items which pertain to the entire table.java.lang.Object[]
getRow(long irow)
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.java.net.URL
getURL()
Initially returns null to indicate that this table itself is not persistent.boolean
isRandom()
Indicates whether random access is provided by this table.void
setName(java.lang.String name)
Sets the name of this table.void
setParameter(DescribedValue dval)
Adds the given DescribedValue to the list of parameter metadata objects associated with this table.void
setURL(java.net.URL url)
Sets the URL of this table.java.lang.String
toString()
Returns an indication of the wrapper structure of this table.
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Field Detail
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baseTable
protected StarTable baseTable
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Constructor Detail
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WrapperStarTable
public WrapperStarTable(StarTable baseTable)
Constructs a new WrapperStarTable from a given base table.- Parameters:
baseTable
- the table to which methods invoked upon the new wrapper table will be forwarded
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Method Detail
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getBaseTable
public StarTable getBaseTable()
Returns the base table underlying this wrapper table.- Returns:
- the table to which methods invoked upon this wrappter table are forwarded
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getColumnCount
public int getColumnCount()
Description copied from interface:StarTable
Returns the number of columns in this table.- Specified by:
getColumnCount
in interfaceStarTable
- Returns:
- the number of columns
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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
- Returns:
- the number of rows, or -1
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getURL
public java.net.URL getURL()
Initially returns null to indicate that this table itself is not persistent.
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setURL
public void setURL(java.net.URL url)
Description copied from interface:StarTable
Sets the URL of this table. It ought to be possible in principle to reconstruct this table by reading the resource at url. If called, the supplied url should provide the return value for subsequent calls ofStarTable.getURL()
.
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getName
public java.lang.String getName()
Description copied from interface:StarTable
Returns the name of this table, if it has one. The meaning of the name is not defined, but it will typically be a short string of text indicating the identity of this table.
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setName
public void setName(java.lang.String name)
Description copied from interface:StarTable
Sets the name of this table. If called, the supplied name should provide the return value for subsequent calls ofStarTable.getName()
.
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getParameters
public java.util.List<DescribedValue> getParameters()
Description copied from interface:StarTable
Returns a list of table parameters, that is metadata items which pertain to the entire table.- Specified by:
getParameters
in interfaceStarTable
- Returns:
- a List of DescribedValue objects constituting table-wide metadata not covered elsewhere in this interface
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getParameterByName
public DescribedValue getParameterByName(java.lang.String parname)
Description copied from interface:StarTable
Returns a parameter (table-wide metadata item) of this table located by its name. If more than one parameter with the given name exists, an arbitrary one will be returned. If no parameter with the given name exists, null will be returned.- Specified by:
getParameterByName
in interfaceStarTable
- Parameters:
parname
- the name of the table parameter required
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setParameter
public void setParameter(DescribedValue dval)
Description copied from interface:StarTable
Adds the given DescribedValue to the list of parameter metadata objects associated with this table. If an item in the parameter list with the same name as the supplied value already exists, it is removed from the list.- Specified by:
setParameter
in interfaceStarTable
- Parameters:
dval
- the new parameter datum to add
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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 interfaceStarTable
- Parameters:
icol
- the column for which header information is required- Returns:
- a ValueInfo object for column icol
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getColumnAuxDataInfos
public java.util.List<ValueInfo> getColumnAuxDataInfos()
Description copied from interface:StarTable
Returns an ordered list of ValueInfo objects representing the auxiliary metadata returned by getColumnInfo(int).getAuxData() calls. The idea is that the resulting list can be used to find out the kind of per-column metadata which can be expected to be found in some or all columns of this table. Each item in the returned list should have a unique name, and other characteristics which are applicable to auxData items which may be returned from any of the columns in this table.The order of the list may indicate some sort of natural ordering of these keys. The returned list is not guaranteed to be complete; it is legal to return an empty list if nothing is known about auxiliary metadata. The list ought not to contain duplicate elements.
- Specified by:
getColumnAuxDataInfos
in interfaceStarTable
- Returns:
- an unmodifiable ordered set of known metadata keys
- See Also:
DefaultValueInfo.getAuxData()
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getRowSequence
public RowSequence getRowSequence() throws java.io.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 interfaceStarTable
- Returns:
- new RowSequence
- Throws:
java.io.IOException
- if there is an error providing access
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getRowAccess
public RowAccess getRowAccess() throws java.io.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 interfaceStarTable
- Returns:
- new RowAccess
- Throws:
java.io.IOException
- if there is an error setting up access
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getRowSplittable
public RowSplittable getRowSplittable() throws java.io.IOException
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
- Returns:
- new RowSplittable
- Throws:
java.io.IOException
- See Also:
RowRunner
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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.
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getCell
public java.lang.Object getCell(long irow, int icol) throws java.io.IOException
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.
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getRow
public java.lang.Object[] getRow(long irow) throws java.io.IOException
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.
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close
public void close() throws java.io.IOException
Description copied from interface:StarTable
Relinquishes any resources associated with this table. This may do nothing, and calling it is often not required, but it provides an opportunity to force release of file descriptors or other resources that are not well handled by garbage collection if the table itself holds them. It is not intended for release of heap-based resources, for which garbage collection already provides adequate management.Following a call to this method, any attempt to use this table or objects such as RowSequences obtained from it will result in undefined behaviour.
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checkedLongToInt
public static int checkedLongToInt(long lval)
Convenience method to get an int value from a long. InvokesTables.checkedLongToInt(long)
.
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toString
public java.lang.String toString()
Returns an indication of the wrapper structure of this table.- Overrides:
toString
in classjava.lang.Object
- Returns:
- string representation
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