org.apache.commons.collections.comparators

Class ComparableComparator

Implemented Interfaces:
Comparator, Serializable

public class ComparableComparator
extends java.lang.Object
implements Comparator, Serializable

A Comparator that compares Comparable objects.

This Comparator is useful, for example, for enforcing the natural order in custom implementations of SortedSet and SortedMap.

Note: In the 2.0 and 2.1 releases of Commons Collections, this class would throw a ClassCastException if either of the arguments to compare were null, not Comparable, or for which compareTo gave inconsistent results. This is no longer the case. See compare for details.

Version:
$Revision: 1.15 $ $Date: 2004/05/15 13:24:11 $
Author:
Henri Yandell
Since:
Commons Collections 2.0
See Also:
java.util.Collections.reverseOrder()

Constructor Summary

ComparableComparator()
Constructor whose use should be avoided.

Method Summary

int
compare(Object obj1, Object obj2)
Compare the two Comparable arguments.
boolean
equals(Object object)
Returns true iff that Object is is a Comparator whose ordering is known to be equivalent to mine.
static ComparableComparator
getInstance()
Gets the singleton instance of a ComparableComparator.
int
hashCode()
Implement a hash code for this comparator that is consistent with equals.

Constructor Details

ComparableComparator

public ComparableComparator()

Method Details

compare

public int compare(Object obj1,
                   Object obj2)
Compare the two Comparable arguments. This method is equivalent to:
((Comparable)obj1).compareTo(obj2)
Parameters:
obj1 - the first object to compare
obj2 - the second object to compare
Returns:
negative if obj1 is less, positive if greater, zero if equal

equals

public boolean equals(Object object)
Returns true iff that Object is is a Comparator whose ordering is known to be equivalent to mine.

This implementation returns true iff object.getClass() equals this.getClass(). Subclasses may want to override this behavior to remain consistent with the Comparator.equals(Object) contract.

Parameters:
object - the object to compare with
Returns:
true if equal
Since:
Commons Collections 3.0

getInstance

public static ComparableComparator getInstance()
Gets the singleton instance of a ComparableComparator.

Developers are encouraged to use the comparator returned from this method instead of constructing a new instance to reduce allocation and GC overhead when multiple comparable comparators may be used in the same VM.

Returns:
the singleton ComparableComparator

hashCode

public int hashCode()
Returns:
a hash code for this comparator.
Since:
Commons Collections 3.0

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