public class

ComparableComparator

extends Object
implements Serializable Comparator<T>
java.lang.Object
   ↳ org.apache.commons.collections.comparators.ComparableComparator

Class Overview

A Comparator Comparator that compares Comparable 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 Comparable, or for which compareTo gave inconsistent results. This is no longer the case. See compare for details.

See Also

Summary

Public Constructors
ComparableComparator()
Constructor whose use should be avoided.
Public Methods
int compare(Object obj1, Object obj2)
Compare the two Comparable 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.
[Expand]
Inherited Methods
From class java.lang.Object
From interface java.util.Comparator

Public Constructors

public ComparableComparator ()

Constructor whose use should be avoided.

Please use the getInstance() method whenever possible.

Public Methods

public int compare (Object obj1, Object obj2)

Compare the two Comparable 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
Throws
NullPointerException when obj1 is null, or when ((Comparable)obj1).compareTo(obj2) does
ClassCastException when obj1 is not a Comparable, or when ((Comparable)obj1).compareTo(obj2) does

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 equals(Object) contract.

Parameters
object the object to compare with
Returns
  • true if equal

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

public int hashCode ()

Implement a hash code for this comparator that is consistent with equals.

Returns
  • a hash code for this comparator.