Package org.apache.sis.util.collection
Class TableColumn<V>
- Object
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- TableColumn<V>
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- Type Parameters:
V
- base type of all values in the column identified by this instance.
- All Implemented Interfaces:
CheckedContainer<V>
public class TableColumn<V> extends Object implements CheckedContainer<V>
Identifies a column inTreeTable.Node
instances. EachTableColumn
instance contains the column header and the type of values for a particular column.TableColumn
s are used for fetching values from nodes as in the following example:public class CityLocation { public static final ColumnTable<String> CITY_NAME = new ColumnTable<>(String.class, "City name"); public static final ColumnTable<Float> LATITUDE = new ColumnTable<>(Float.class, "Latitude"); public static final ColumnTable<Float> LONGITUDE = new ColumnTable<>(Float.class, "Longitude"); private String name; private float latitude; private float longitude; CityLocation(TreeTable.Node myNode) { name = myNode.getValue(CITY_NAME); latitude = myNode.getValue(LATITUDE); longitude = myNode.getValue(LONGITUDE); } }
Identity comparisons and serializationThis base class relies on identity comparisons instead than defining theequals(Object)
method, because the element type is not a sufficient criterion for differentiating the columns (many columns have values of the same type) and the header is arbitrary. Consequently developers who create their own instances are encouraged to declare them as static final constants as in the above example, and use those constants consistently.This base class is not serializable because the default deserialization mechanism does not resolve automatically the deserialized instances to the above-cited singleton instances. Developers who need serialization support for their own instances have to resolve them in their own subclass. The following example is one possible way to achieve that goal:
The constants defined in this class use a similar approach for providing serialization support.public class CityLocation { public static final ColumnTable<String> CITY_NAME = new Column<>("CITY_NAME", String.class, "City name"); public static final ColumnTable<Float> LATITUDE = new Column<>("LATITUDE", Float.class, "Latitude"); public static final ColumnTable<Float> LONGITUDE = new Column<>("LONGITUDE", Float.class, "Longitude"); private static final class Column<V> extends TableColumn<V> implements Serializable { private final String field; private Column(String field, Class<V> type, CharSequence header) { super(type, header); this.field = field; } private Object readResolve() throws ObjectStreamException { try { return CityLocation.class.getField(field).get(null); } catch (Exception cause) { // Many exceptions, including unchecked ones. throw new InvalidObjectException(cause.toString()); } } } }
- Since:
- 0.3
Defined in the
sis-utility
module
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Field Summary
Fields Modifier and Type Field Description static TableColumn<String>
IDENTIFIER
Frequently-used constant for a column of object identifiers.static TableColumn<Integer>
INDEX
Frequently-used constant for a column of index values.static TableColumn<CharSequence>
NAME
Frequently-used constant for a column of object names.static TableColumn<CharSequence>
REMARKS
Frequently-used constant for a column of remarks.static TableColumn<Class<?>>
TYPE
Frequently-used constant for a column of object types.static TableColumn<Object>
VALUE
Frequently-used constant for a column of object values.static TableColumn<Number>
VALUE_AS_NUMBER
Frequently-used constant for a column of object numerical values.static TableColumn<CharSequence>
VALUE_AS_TEXT
Frequently-used constant for a column of object textual values.
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Constructor Summary
Constructors Modifier Constructor Description protected
TableColumn()
Invoked on deserialization for creating an initially empty instance.TableColumn(Class<V> type, CharSequence header)
Creates a new instance for the given type of values.
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description Class<V>
getElementType()
Returns the base type of all values in any column identified by thisTableColumn
instance.InternationalString
getHeader()
Returns the text to display as column header.String
toString()
Returns a string representation of this table column.
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Field Detail
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NAME
public static final TableColumn<CharSequence> NAME
Frequently-used constant for a column of object names. The column header is "Name" (eventually localized) and the column elements are typically instances ofString
orInternationalString
, depending on whether the data provide localization support or not.
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IDENTIFIER
public static final TableColumn<String> IDENTIFIER
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INDEX
public static final TableColumn<Integer> INDEX
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TYPE
public static final TableColumn<Class<?>> TYPE
Frequently-used constant for a column of object types. The column header is "Type" (eventually localized).
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VALUE
public static final TableColumn<Object> VALUE
Frequently-used constant for a column of object values. The column header is "Value" (eventually localized) and the column elements can be instance of any kind of objects.- See Also:
VALUE_AS_TEXT
,VALUE_AS_NUMBER
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VALUE_AS_TEXT
public static final TableColumn<CharSequence> VALUE_AS_TEXT
Frequently-used constant for a column of object textual values. The column header is "Value" (eventually localized) and the column elements are typically instances ofString
orInternationalString
, depending on whether the data provide localization support or not.
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VALUE_AS_NUMBER
public static final TableColumn<Number> VALUE_AS_NUMBER
Frequently-used constant for a column of object numerical values. The column header is "Value" (eventually localized).
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REMARKS
public static final TableColumn<CharSequence> REMARKS
Frequently-used constant for a column of remarks. The column header is "Remarks" (eventually localized) and the column elements are typically instances ofString
orInternationalString
, depending on whether the data provide localization support or not.- Since:
- 1.0
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Constructor Detail
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TableColumn
protected TableColumn()
Invoked on deserialization for creating an initially empty instance. This constructor hasprotected
visibility only because the Java deserialization mechanism requires so; this constructor shall not be invoked in any other context. See the Identity comparisons and serialization section in the class javadoc for more information.
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TableColumn
public TableColumn(Class<V> type, CharSequence header)
Creates a new instance for the given type of values.- Parameters:
type
- base type of all values in the column identified by this instance.header
- the text to display as column header.
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Method Detail
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getHeader
public InternationalString getHeader()
Returns the text to display as column header.- Returns:
- the text to display as column header.
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getElementType
public final Class<V> getElementType()
Returns the base type of all values in any column identified by thisTableColumn
instance.- Specified by:
getElementType
in interfaceCheckedContainer<V>
- Returns:
- the element type.
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