Package uk.ac.starlink.table
Class ColumnData
- java.lang.Object
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- uk.ac.starlink.table.ColumnData
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- Direct Known Subclasses:
ArrayColumn
,BlankColumn
,ConstantColumn
,WrapperColumn
public abstract class ColumnData extends java.lang.Object
A column which can supply and possibly store cells in array-like storage as well as supply column metadata. Note there is nothing in this class which describes the number of elements it contains (length of the column). Columns are intended to be managed by tables, and it is the table which should keep track of this information.- Author:
- Mark Taylor (Starlink)
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Constructor Summary
Constructors Constructor Description ColumnData()
Constructs a new ColumnData with no metadata.ColumnData(ColumnInfo colinfo)
Constructs a new ColumnData with metadata supplied by a given ColumnInfo object.ColumnData(ValueInfo base)
Performs ColumnData initialisation based on template ValueInfo object.
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Method Summary
All Methods Instance Methods Abstract Methods Concrete Methods Modifier and Type Method Description ColumnInfo
getColumnInfo()
Returns the ColumnInfo which provides the metadata for this column.boolean
isWritable()
Indicates whether this object can store values.abstract java.lang.Object
readValue(long irow)
Returns the value stored at a given row in this column.void
setColumnInfo(ColumnInfo colinfo)
Sets the ColumnInfo which provides the metadata for this column.void
storeValue(long irow, java.lang.Object val)
Stores a given value in a given row for this column.
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Constructor Detail
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ColumnData
public ColumnData()
Constructs a new ColumnData with no metadata.
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ColumnData
public ColumnData(ColumnInfo colinfo)
Constructs a new ColumnData with metadata supplied by a given ColumnInfo object.- Parameters:
colinfo
- the column metadata
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ColumnData
public ColumnData(ValueInfo base)
Performs ColumnData initialisation based on template ValueInfo object.- Parameters:
base
- template
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Method Detail
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getColumnInfo
public ColumnInfo getColumnInfo()
Returns the ColumnInfo which provides the metadata for this column.- Returns:
- the column metadata
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setColumnInfo
public void setColumnInfo(ColumnInfo colinfo)
Sets the ColumnInfo which provides the metadata for this column.- Parameters:
colinfo
- the column metadata
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readValue
public abstract java.lang.Object readValue(long irow) throws java.io.IOException
Returns the value stored at a given row in this column.- Parameters:
irow
- the row from which to retrieve the value- Returns:
- the value stored at irow
- Throws:
java.io.IOException
- if there is some problem reading
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storeValue
public void storeValue(long irow, java.lang.Object val) throws java.io.IOException
Stores a given value in a given row for this column. Will only work if the isWritable method returns true. The implementation in the ColumnData class throws an UnsupportedOperationException.- Parameters:
val
- the object to storeirow
- the row to store it in- Throws:
java.lang.UnsupportedOperationException
- if !isWritable()
java.lang.NullPointerException
- if val==null and this column is not nullablejava.lang.ArrayStoreException
- if val is not compatible with the content class of this columnjava.io.IOException
- if there is some problem writing
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isWritable
public boolean isWritable()
Indicates whether this object can store values. The implementation in the ColumnData class returns false- Returns:
- true iff
storeValue(long, java.lang.Object)
can be used
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