org.apache.commons.collections.comparators

Class NullComparator

java.lang.Object
|
+--org.apache.commons.collections.comparators.NullComparator

All Implemented Interfaces:
Comparator, Serializable

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

A Comparator that will compare nulls to be either lower or higher than other objects.

Since:

Commons Collections 2.0

Author:

Michael A. Smith

Constructor Summary

NullComparator()

Construct an instance that sorts null higher than any non-null object it is compared with.

NullComparator(Comparator nonNullComparator)

Construct an instance that sorts null higher than any non-null object it is compared with.

NullComparator(boolean nullsAreHigh)

Construct an instance that sorts null higher or lower than any non-null object it is compared with.

NullComparator(Comparator nonNullComparator, boolean nullsAreHigh)

Construct an instance that sorts null higher or lower than any non-null object it is compared with.

Method Summary

int

compare(Object o1, Object o2)

Perform a comparison between two objects.

boolean

equals(Object obj)

Determines whether the specified object represents a comparator that is equal to this comparator.

int

hashCode()

Implement a hash code for this comparator that is consistent with #equals(Object).

Constructor Details

NullComparator

public NullComparator()

Construct an instance that sorts null higher than any non-null object it is compared with. When comparing two non-null objects, the ComparableComparator is used.

NullComparator

public NullComparator(boolean nullsAreHigh)

Construct an instance that sorts null higher or lower than any non-null object it is compared with. When comparing two non-null objects, the ComparableComparator is used.

Parameters:

nullsAreHigh - a true value indicates that null should be compared as higher than a non-null object.

NullComparator

public NullComparator(Comparator nonNullComparator, boolean nullsAreHigh)

Construct an instance that sorts null higher or lower than any non-null object it is compared with. When comparing two non-null objects, the specified Comparator is used.

Parameters:

nonNullComparator - the comparator to use when comparing two non-null objects.
nullsAreHigh - a true value indicates that null should be compared as higher than a non-null object.

Throws:

- if nonNullComparator is null

NullComparator
public  NullComparator(Comparator nonNullComparator)
  Construct an instance that sorts null higher than any
  non-null object it is compared with.  When comparing two
  non-null objects, the specified Comparator is
  used.
Parameters:
nonNullComparator - the comparator to use when comparing two
non-null objects.
Throws:
 - if nonNullComparator is
null
Method Detailscompare
public int compare(Object o1, Object o2)
  Perform a comparison between two objects.  If both objects are
  null, a 0 value is returned.  If one object
  is null and the other is not, the result is determined on
  whether the Comparator was constructed to have nulls as higher or lower
  than other objects.  If neither object is null, an
  underlying comparator specified in the constructor (or the default) is
  used to compare the non-null objects.
Parameters:
o1 - the first object to compare
o2 - the object to compare it to.
Returns:
-1 if o1 is "lower" than (less than,
before, etc.) o2; 1 if o1 is
"higher" than (greater than, after, etc.) o2; or
0 if o1 and o2 are equal.
equals
public boolean equals(Object obj)
  Determines whether the specified object represents a comparator that is
  equal to this comparator.
Parameters:
obj - the object to compare this comparator with.
Returns:
true if the specified object is a NullComparator
with equivalent null comparison behavior
(i.e. null high or low) and with equivalent underlying
non-null object comparators.
hashCode
public int hashCode()  Implement a hash code for this comparator that is consistent with
equals(Object).
Returns:
a hash code for this comparator.
Generated on
  February 15, 2004
  by GNU Classpath Tools (Gjdoc XmlDoclet 0.6.1).