Package org.springframework.util.comparator

Class NullSafeComparator<T>

java.lang.Object

org.springframework.util.comparator.NullSafeComparator<T>

Type Parameters:

T - the type of objects that may be compared by this comparator

All Implemented Interfaces:

Comparator<T>

public class NullSafeComparator<T>
extends Object
implements Comparator<T>

A Comparator that will safely compare nulls to be lower or higher than other objects. Can decorate a given Comparator or work on Comparables.

Since:

1.2.2

Author:

Keith Donald, Juergen Hoeller

See Also:

• Comparable

Field Summary

Fields

Modifier and Type	Field	Description
static final NullSafeComparator	NULLS_HIGH	A shared default instance of this comparator, treating nulls higher than non-null objects.
static final NullSafeComparator	NULLS_LOW	A shared default instance of this comparator, treating nulls lower than non-null objects.

Constructor Summary

Constructors

Constructor	Description
NullSafeComparator(Comparator<T> comparator, boolean nullsLow)	Create a NullSafeComparator that sorts null based on the provided flag, decorating the given Comparator.

Method Summary

Modifier and Type	Method	Description
int	compare(T o1, T o2)
boolean	equals(Object other)
int	hashCode()
String	toString()

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Methods inherited from interface java.util.Comparator

reversed, thenComparing, thenComparing, thenComparing, thenComparingDouble, thenComparingInt, thenComparingLong

Field Details

NULLS_LOW

public static final NullSafeComparator NULLS_LOW

A shared default instance of this comparator, treating nulls lower than non-null objects.

See Also:

• Comparators.nullsLow()

NULLS_HIGH

public static final NullSafeComparator NULLS_HIGH

A shared default instance of this comparator, treating nulls higher than non-null objects.

See Also:

• Comparators.nullsHigh()

Constructor Details

NullSafeComparator

public NullSafeComparator(Comparator<T> comparator,
 boolean nullsLow)

Create a NullSafeComparator that sorts null based on the provided flag, decorating the given Comparator.

When comparing two non-null objects, the specified Comparator will be used. The given underlying Comparator must be able to handle the elements that this Comparator will be applied to.

Parameters:

comparator - the comparator to use when comparing two non-null objects

nullsLow - whether to treat nulls lower or higher than non-null objects

Method Details

compare

public int compare(@Nullable
 T o1,
 @Nullable
 T o2)

Specified by:

compare in interface Comparator<T>

equals

public boolean equals(@Nullable
 Object other)

Specified by:

equals in interface Comparator<T>

Overrides:

equals in class Object

hashCode

public int hashCode()

Overrides:

hashCode in class Object

toString

public String toString()

Overrides:

toString in class Object