org.knime.core.data
Class DataValueComparator

java.lang.Object
  org.knime.core.data.DataValueComparator

All Implemented Interfaces:

Comparator<DataCell>

Direct Known Subclasses:

ComplexNumberValueComparator, DateAndTimeComparator, DoubleValueComparator, FuzzyIntervalValueComparator, FuzzyNumberValueComparator, GeneralDataValueComparator, IntervalValueComparator, IntValueComparator, LongValueComparator, PNGImageValueComparator, PortObjectValueComparator, StringValueComparator, TimestampValue.TimestampValueComparator

public abstract class DataValueComparator
extends Object
implements Comparator<DataCell>

The comparator used to compare two DataValue objects. An instance of this class is returned by each DataValue.UtilityFactory implementation. Implementations can safely assume that objects passed to the compareDataValues(DataValue, DataValue) method support a type cast to that type of the DataValue returning this comparator.

Note: this comparator imposes orderings that are inconsistent with equals. That is, the return value zero is not equivalent to equals returning true, it rather says "don't know". Meaning, if two DataValues cannot be compared (because they represent completely different value types) the comparator will return zero - and equals will return false.)

Author:

Michael Berthold, University of Konstanz

See Also:

DataValue.UtilityFactory.getComparator()

Constructor Summary

protected

DataValueComparator() Create a new DataValue comparator.

Method Summary

int	compare(DataCell c1, DataCell c2) This final implementation checks and handles DataCells representing missing values, before it delegates the actual comparison to the derived class, by calling compareDataValues(DataValue, DataValue).
protected abstract int	compareDataValues(DataValue v1, DataValue v2) Do not call this function, rather call the compare(DataCell, DataCell) method, which handles missing cells.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface java.util.Comparator

equals

Constructor Detail

DataValueComparator

protected DataValueComparator()

Create a new DataValue comparator. This constructor does nothing.

Method Detail

compare

public final int compare(DataCell c1,
                         DataCell c2)

This final implementation checks and handles DataCells representing missing values, before it delegates the actual comparison to the derived class, by calling compareDataValues(DataValue, DataValue). Missing cells are considered to be smaller than any other non-missing DataCell, and two missing cells are not comparable (returns 0). Note: return value 0 is not equivalent to c1 equals c2, rather they are not comparable at all.

Specified by:

compare in interface Comparator<DataCell>

Parameters:

c1 - the first DataCell to compare the other with

c2 - the other DataCell to compare the first with

Returns:

a negative number if c1 is smaller than c2, a positive number if c1 is larger than c2, otherwise zero

Throws:

NullPointerException - if any of the objects is null

See Also:

Comparator.compare(java.lang.Object, java.lang.Object), compareDataValues(DataValue, DataValue)

compareDataValues

protected abstract int compareDataValues(DataValue v1,
                                         DataValue v2)

Do not call this function, rather call the compare(DataCell, DataCell) method, which handles missing cells. The derived class should compare the two passed DataValues. It can be safely assumed that both values are castable to the specific type of the DataValue that returned this comparator.

Parameters:

v1 - the first DataValue to compare the other with

v2 - the other DataValue to compare the first with

Returns:

return -1 if v1 is smaller than v2, +1 if v1 is larger than v2, 0 otherwise