net.innig.collect
Class ListDiff

java.lang.Object
  net.innig.collect.CollectionDiff
      net.innig.collect.ListDiff

public class ListDiff
extends CollectionDiff

Finds the difference between two ordered lists. Given a pair of lists, ListDiff provides a sequence of steps which will mutate the first list into the second. These steps implement ListDiff.Step, and include insert, move, and remove. You can ask for the steps using getSteps(), or call applySteps to have the ListDiff walk a ListMutator through the steps.

ListDiff is useful for situations where some structure (such as a user interface) is shadowing a changing list, and you don't want to rebuild the structure from scratch every time the list changes -- perhaps beacuse the cost of recreating the structure is high, or because you don't want to lose state information about existing elements whose position has changed in the list.

The algorithm ListDiff uses for generating the steps is quite simple. It does not guarantee the shortest possible sequence of steps, but usually comes quite close.

Maturity: This is a mature API, and a stable implementation. It performs well in informal testing, but has not undergone methodical or real-world testing.

Plans: There are no current plans to expand or revise this class's functionality. It would be worth researching alternative algorithms for generating the steps.

Version:

[Development version]

Author:

Paul Cantrell

Nested Class Summary

class	ListDiff.Insert A list transformation step: insert an object at a given position.
class	ListDiff.Move A list transformation step: move an object from one position to another.
class	ListDiff.Remove A list transformation step: remove an object at a given position.
class	ListDiff.Step A step in a list transformation.

Constructor Summary

ListDiff(java.util.List oldStuff, java.util.List newStuff)
Prepares a comparison of two lists.

Method Summary

void	applySteps(ListMutator mutator) Walks a ListMutator through the sequence of steps which transform the old list into the new.
boolean	equals(java.lang.Object other) Returns true if the other object is a list diff comparing equal lists.
java.util.Iterator	getSteps() Returns a sequence of steps which transform the old list into the new.
static void	main(java.lang.String[] args) For testing

Methods inherited from class net.innig.collect.CollectionDiff

getAdded, getRemoved, getSame, hashCode, sameElements

Methods inherited from class java.lang.Object

getClass, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

ListDiff

public ListDiff(java.util.List oldStuff,
                java.util.List newStuff)

Prepares a comparison of two lists.

Method Detail

main

public static void main(java.lang.String[] args)
                 throws java.lang.Exception

For testing

Throws:

java.lang.Exception

getSteps

public java.util.Iterator getSteps()

Returns a sequence of steps which transform the old list into the new. The Iterator returns ListDiff.Step objects.

applySteps

public void applySteps(ListMutator mutator)

Walks a ListMutator through the sequence of steps which transform the old list into the new.

equals

public boolean equals(java.lang.Object other)

Returns true if the other object is a list diff comparing equal lists.

Overrides:

equals in class CollectionDiff