public class

NullComparator

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

Class Overview

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

Summary

Public Constructors
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.
Public Methods
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).
[Expand]
Inherited Methods
From class java.lang.Object
From interface java.util.Comparator

Public Constructors

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.

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. This argument cannot be null
Throws
NullPointerException if nonNullComparator is null

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. A false value indicates that null should be compared as lower than a non-null object.

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. This argument cannot be null
nullsAreHigh a true value indicates that null should be compared as higher than a non-null object. A false value indicates that null should be compared as lower than a non-null object.
Throws
NullPointerException if nonNullComparator is null

Public Methods

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.

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.

public int hashCode ()

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

Returns
  • a hash code for this comparator.