edu.nrao.sss.sort
Class ReflectiveEnumSortKey<T,E extends Enum<E>>

java.lang.Object
  edu.nrao.sss.sort.SortKey<E>
      edu.nrao.sss.sort.EnumSortKey<E>
          edu.nrao.sss.sort.ReflectiveEnumSortKey<T,E>

All Implemented Interfaces:

Orderable, Comparator<T>

public final class ReflectiveEnumSortKey<T,E extends Enum<E>>
extends EnumSortKey<E>
implements Comparator<T>

A sort key and comparator that works with the enumeration elements returned by a method that is found reflectively.

Clients of this class must provide the name of a public, no argument, method that returns an Enum and that is present in classes of the parameterized type T. The method created from that name is called on the objects to be compared, and the enumeration elements returned from those methods are what is actually compared.

Because this class is a SortKey, you may configure its instances with a particular SortOrder. Because it is also an EnumSortKey, you may specify a custom ordering. You may place instances of this class in a CompoundComparator.

Example
Let there be a class, Person, that has the following attributes, each of which is an enumeration: gender and handedness. Furthermore, assume the normal convention for the getters (e.g., getGender()). If you are studying the distribution of handedness by age and gender, you might want to sort a collection of people by age, gender, and handedness. You could do this without writing any new classes by doing as follows:

   ReflectiveIntSortKey<Person> ageKey =
     new ReflectiveIntSortKey<Person>("getAge");
     
   ReflectiveEnumSortKey<Person,Gender> sexKey =
     new ReflectiveEnumSortKey<Person,Gender>("getGender");
     
   ReflectiveEnumSortKey<Person,Handedness> handKey =
     new ReflectiveEnumSortKey<Person,Handedness>("getHandedness");
     
   CompoundComparator<Person> comparator =
     new CompoundComparator<Person>(ageKey, sexKey, handKey);
     
   Collections.sort(population, comparator);
 

Version Info:

$Revision: 593 $

$Date: 2007-05-07 15:54:14 -0600 (Mon, 07 May 2007) $

$Author: dharland $

Since:

2007-05-07

Author:

David M. Harland

Constructor Summary

ReflectiveEnumSortKey(String methodName)
Creates a new instance that will base its comparison on the Integer returned by the method with the given name.

Method Summary

int	compare(T o1, T o2)
void	setMethodName(String newMethodName) Sets the name of the method used for making comparisons.

Methods inherited from class edu.nrao.sss.sort.EnumSortKey

compareAscending, compareCustom, compareNatural, compareObjects, setCustomOrder

Methods inherited from class edu.nrao.sss.sort.SortKey

compareObjects, getOrder, nullOrdering, objectsAreEqual, setOrder

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

equals

Constructor Detail

ReflectiveEnumSortKey

public ReflectiveEnumSortKey(String methodName)

Creates a new instance that will base its comparison on the Integer returned by the method with the given name.

Parameters:

methodName - the name of a public, no argument, method that belongs to objects of type T and that returns an Enum). If there is any trouble creating or calling the method with this name, it will be treated as if it returns null.

Method Detail

setMethodName

public void setMethodName(String newMethodName)

Sets the name of the method used for making comparisons.

Parameters:

newMethodName - the name of a public, no argument, method that belongs to objects of type T and that returns an Integer (or in). If there is any trouble creating or calling the method with this name, it will be treated as if it returns a Integer of Integer.MIN_VALUE.

compare

public int compare(T o1,
                   T o2)

Specified by:

compare in interface Comparator<T>