org.springframework.core

Class OrderComparator

java.lang.Object

org.springframework.core.OrderComparator

All Implemented Interfaces:

Comparator<Object>

Direct Known Subclasses:

AnnotationAwareOrderComparator

public class OrderComparator
extends Object
implements Comparator<Object>

Comparator implementation for Ordered objects, sorting by order value ascending, respectively by priority descending.

PriorityOrdered Objects

PriorityOrdered objects will be sorted with higher priority than plain Ordered objects.

Same Order Objects

Objects that have the same order value will be sorted with arbitrary ordering with respect to other objects with the same order value.

Non-ordered Objects

Any object that does not provide its own order value is implicitly assigned a value of Ordered.LOWEST_PRECEDENCE, thus ending up at the end of a sorted collection in arbitrary order with respect to other objects with the same order value.

Since:

07.04.2003

Author:

Juergen Hoeller, Sam Brannen

See Also:

Ordered, PriorityOrdered, AnnotationAwareOrderComparator, List.sort(java.util.Comparator), Arrays.sort(Object[], java.util.Comparator)

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static interface	OrderComparator.OrderSourceProvider Strategy interface to provide an order source for a given object.

Field Summary

Fields

Modifier and Type	Field and Description
static OrderComparator	INSTANCE Shared default instance of OrderComparator.

Constructor Summary

Constructors

Constructor and Description
OrderComparator()

Method Summary

Modifier and Type	Method and Description
int	compare(Object o1, Object o2)
protected Integer	findOrder(Object obj) Find an order value indicated by the given object.
protected int	getOrder(Object obj) Determine the order value for the given object.
Integer	getPriority(Object obj) Determine a priority value for the given object, if any.
static void	sort(List<?> list) Sort the given List with a default OrderComparator.
static void	sort(Object[] array) Sort the given array with a default OrderComparator.
static void	sortIfNecessary(Object value) Sort the given array or List with a default OrderComparator, if necessary.
Comparator<Object>	withSourceProvider(OrderComparator.OrderSourceProvider sourceProvider) Build an adapted order comparator with the given source provider.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface java.util.Comparator

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

Field Detail

INSTANCE

public static final OrderComparator INSTANCE

Shared default instance of OrderComparator.

Constructor Detail

OrderComparator

public OrderComparator()

Method Detail

withSourceProvider

public Comparator<Object> withSourceProvider(OrderComparator.OrderSourceProvider sourceProvider)

Build an adapted order comparator with the given source provider.

Parameters:

sourceProvider - the order source provider to use

Returns:

the adapted comparator

Since:

4.1

compare

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

Specified by:

compare in interface Comparator<Object>

getOrder

protected int getOrder(@Nullable
                       Object obj)

Determine the order value for the given object.

The default implementation checks against the Ordered interface through delegating to findOrder(java.lang.Object). Can be overridden in subclasses.

Parameters:

obj - the object to check

Returns:

the order value, or Ordered.LOWEST_PRECEDENCE as fallback

findOrder

@Nullable
protected Integer findOrder(Object obj)

Find an order value indicated by the given object.

The default implementation checks against the Ordered interface. Can be overridden in subclasses.

Parameters:

obj - the object to check

Returns:

the order value, or null if none found

getPriority

@Nullable
public Integer getPriority(Object obj)

Determine a priority value for the given object, if any.

The default implementation always returns null. Subclasses may override this to give specific kinds of values a 'priority' characteristic, in addition to their 'order' semantics. A priority indicates that it may be used for selecting one object over another, in addition to serving for ordering purposes in a list/array.

Parameters:

obj - the object to check

Returns:

the priority value, or null if none

Since:

4.1

sort

public static void sort(List<?> list)

Sort the given List with a default OrderComparator.

Optimized to skip sorting for lists with size 0 or 1, in order to avoid unnecessary array extraction.

Parameters:

list - the List to sort

See Also:

List.sort(java.util.Comparator)

sort

public static void sort(Object[] array)

Sort the given array with a default OrderComparator.

Optimized to skip sorting for lists with size 0 or 1, in order to avoid unnecessary array extraction.

Parameters:

array - the array to sort

See Also:

Arrays.sort(Object[], java.util.Comparator)

sortIfNecessary

public static void sortIfNecessary(Object value)

Sort the given array or List with a default OrderComparator, if necessary. Simply skips sorting when given any other value.

Optimized to skip sorting for lists with size 0 or 1, in order to avoid unnecessary array extraction.

Parameters:

value - the array or List to sort

See Also:

Arrays.sort(Object[], java.util.Comparator)