org.springframework.util.comparator

Class CompoundComparator<T>

java.lang.Object

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

All Implemented Interfaces:

java.io.Serializable, java.util.Comparator<T>

public class CompoundComparator<T>
extends java.lang.Object
implements java.util.Comparator<T>, java.io.Serializable

A comparator that chains a sequence of one or more Comparators.

A compound comparator calls each Comparator in sequence until a single Comparator returns a non-zero result, or the comparators are exhausted and zero is returned.

This facilitates in-memory sorting similar to multi-column sorting in SQL. The order of any single Comparator in the list can also be reversed.

Since:

1.2.2

Author:

Keith Donald, Juergen Hoeller

See Also:

Serialized Form

Constructor Summary

Constructors

Constructor and Description
CompoundComparator() Construct a CompoundComparator with initially no Comparators.
CompoundComparator(java.util.Comparator... comparators) Construct a CompoundComparator from the Comparators in the provided array.

Method Summary

Modifier and Type	Method and Description
void	addComparator(java.util.Comparator<? extends T> comparator) Add a Comparator to the end of the chain.
void	addComparator(java.util.Comparator<? extends T> comparator, boolean ascending) Add a Comparator to the end of the chain using the provided sort order.
int	compare(T o1, T o2)
boolean	equals(java.lang.Object obj)
int	getComparatorCount() Returns the number of aggregated comparators.
int	hashCode()
void	invertOrder() Invert the sort order of each sort definition contained by this compound comparator.
void	invertOrder(int index) Invert the sort order of the sort definition at the specified index.
void	setAscendingOrder(int index) Change the sort order at the given index to ascending.
void	setComparator(int index, java.util.Comparator<? extends T> comparator) Replace the Comparator at the given index.
void	setComparator(int index, java.util.Comparator<T> comparator, boolean ascending) Replace the Comparator at the given index using the given sort order.
void	setDescendingOrder(int index) Change the sort order at the given index to descending sort.
java.lang.String	toString()

Methods inherited from class java.lang.Object

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

Methods inherited from interface java.util.Comparator

comparing, comparing, comparingDouble, comparingInt, comparingLong, naturalOrder, nullsFirst, nullsLast, reversed, reverseOrder, thenComparing, thenComparing, thenComparing, thenComparingDouble, thenComparingInt, thenComparingLong

Constructor Detail

CompoundComparator

public CompoundComparator()

Construct a CompoundComparator with initially no Comparators. Clients must add at least one Comparator before calling the compare method or an IllegalStateException is thrown.

CompoundComparator

public CompoundComparator(java.util.Comparator... comparators)

Construct a CompoundComparator from the Comparators in the provided array.

All Comparators will default to ascending sort order, unless they are InvertibleComparators.

Parameters:

comparators - the comparators to build into a compound comparator

See Also:

InvertibleComparator

Method Detail

addComparator

public void addComparator(java.util.Comparator<? extends T> comparator)

Add a Comparator to the end of the chain.

The Comparator will default to ascending sort order, unless it is a InvertibleComparator.

Parameters:

comparator - the Comparator to add to the end of the chain

See Also:

InvertibleComparator

addComparator

public void addComparator(java.util.Comparator<? extends T> comparator,
                          boolean ascending)

Add a Comparator to the end of the chain using the provided sort order.

Parameters:

comparator - the Comparator to add to the end of the chain

ascending - the sort order: ascending (true) or descending (false)

setComparator

public void setComparator(int index,
                          java.util.Comparator<? extends T> comparator)

Replace the Comparator at the given index.

The Comparator will default to ascending sort order, unless it is a InvertibleComparator.

Parameters:

index - the index of the Comparator to replace

comparator - the Comparator to place at the given index

See Also:

InvertibleComparator

setComparator

public void setComparator(int index,
                          java.util.Comparator<T> comparator,
                          boolean ascending)

Replace the Comparator at the given index using the given sort order.

Parameters:

index - the index of the Comparator to replace

comparator - the Comparator to place at the given index

ascending - the sort order: ascending (true) or descending (false)

invertOrder

public void invertOrder()

Invert the sort order of each sort definition contained by this compound comparator.

invertOrder

public void invertOrder(int index)

Invert the sort order of the sort definition at the specified index.

Parameters:

index - the index of the comparator to invert

setAscendingOrder

public void setAscendingOrder(int index)

Change the sort order at the given index to ascending.

Parameters:

index - the index of the comparator to change

setDescendingOrder

public void setDescendingOrder(int index)

Change the sort order at the given index to descending sort.

Parameters:

index - the index of the comparator to change

getComparatorCount

public int getComparatorCount()

Returns the number of aggregated comparators.

compare

public int compare(T o1,
                   T o2)

Specified by:

compare in interface java.util.Comparator<T>

equals

public boolean equals(java.lang.Object obj)

Specified by:

equals in interface java.util.Comparator<T>

Overrides:

equals in class java.lang.Object

hashCode

public int hashCode()

Overrides:

hashCode in class java.lang.Object

toString

public java.lang.String toString()

Overrides:

toString in class java.lang.Object