org.incava.util.diff
Class Diff

java.lang.Object
  extended by org.incava.util.diff.Diff
Direct Known Subclasses:
Diff

public class Diff
extends Object

Compares two collections, returning a list of the additions, changes, and deletions between them. A Comparator may be passed as an argument to the constructor, and will thus be used. If not provided, the initial value in the a ("from") collection will be looked at to see if it supports the Comparable interface. If so, its equals and compareTo methods will be invoked on the instances in the "from" and "to" collections; otherwise, for speed, hash codes from the objects will be used instead for comparison.

The file FileDiff.java shows an example usage of this class, in an application similar to the Unix "diff" program.


Field Summary
protected  Object[] a
          The source array, AKA the "from" values.
protected  Object[] b
          The target array, AKA the "to" values.
protected  List<Difference> diffs
          The list of differences, as Difference instances.
 
Constructor Summary
Diff(Collection a, Collection b)
          Constructs the Diff object for the two collections, using the default comparison mechanism between the objects, such as equals and compareTo.
Diff(Collection a, Collection b, Comparator comp)
          Constructs the Diff object for the two collections, using the given comparator.
Diff(Object[] a, Object[] b)
          Constructs the Diff object for the two arrays, using the default comparison mechanism between the objects, such as equals and compareTo.
Diff(Object[] a, Object[] b, Comparator comp)
          Constructs the Diff object for the two arrays, using the given comparator.
 
Method Summary
protected  void append(Integer value)
          Adds the given value to the "end" of the threshold map, that is, with the greatest index/key.
protected  boolean callFinishedA()
          Override and return true in order to have finishedA invoked at the last element in the a array.
protected  boolean callFinishedB()
          Override and return true in order to have finishedB invoked at the last element in the b array.
 List<Difference> diff()
          Runs diff and returns the results.
protected  boolean equals(Object x, Object y)
          Compares the two objects, using the comparator provided with the constructor, if any.
protected  void finishedA(int lastA)
          Invoked at the last element in a, if callFinishedA returns true.
protected  void finishedB(int lastB)
          Invoked at the last element in b, if callFinishedB returns true.
protected  Integer getLastValue()
          Returns the value for the greatest key in the map.
 Integer[] getLongestCommonSubsequences()
          Returns an array of the longest common subsequences.
protected  Integer insert(Integer j, Integer k)
          Inserts the given values into the threshold map.
protected  boolean isGreaterThan(Integer index, Integer val)
          Returns whether the value in the map for the given index is greater than the given value.
protected  boolean isLessThan(Integer index, Integer val)
          Returns whether the value in the map for the given index is less than the given value.
protected static boolean isNonzero(Integer i)
          Returns whether the integer is not zero (including if it is not null).
protected  void onANotB(int ai, int bi)
          Invoked for elements in a and not in b.
protected  void onBNotA(int ai, int bi)
          Invoked for elements in b and not in a.
protected  void onMatch(int ai, int bi)
          Invoked for elements matching in a and b.
protected static Integer[] toArray(TreeMap<Integer,Integer> map)
          Converts the map (indexed by java.lang.Integers) into an array.
protected  void traverseSequences()
          Traverses the sequences, seeking the longest common subsequences, invoking the methods finishedA, finishedB, onANotB, and onBNotA.
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Field Detail

a

protected final Object[] a
The source array, AKA the "from" values.


b

protected final Object[] b
The target array, AKA the "to" values.


diffs

protected List<Difference> diffs
The list of differences, as Difference instances.

Constructor Detail

Diff

public Diff(Object[] a,
            Object[] b,
            Comparator comp)
Constructs the Diff object for the two arrays, using the given comparator.


Diff

public Diff(Object[] a,
            Object[] b)
Constructs the Diff object for the two arrays, using the default comparison mechanism between the objects, such as equals and compareTo.


Diff

public Diff(Collection a,
            Collection b,
            Comparator comp)
Constructs the Diff object for the two collections, using the given comparator.


Diff

public Diff(Collection a,
            Collection b)
Constructs the Diff object for the two collections, using the default comparison mechanism between the objects, such as equals and compareTo.

Method Detail

diff

public List<Difference> diff()
Runs diff and returns the results.


traverseSequences

protected void traverseSequences()
Traverses the sequences, seeking the longest common subsequences, invoking the methods finishedA, finishedB, onANotB, and onBNotA.


callFinishedA

protected boolean callFinishedA()
Override and return true in order to have finishedA invoked at the last element in the a array.


callFinishedB

protected boolean callFinishedB()
Override and return true in order to have finishedB invoked at the last element in the b array.


finishedA

protected void finishedA(int lastA)
Invoked at the last element in a, if callFinishedA returns true.


finishedB

protected void finishedB(int lastB)
Invoked at the last element in b, if callFinishedB returns true.


onANotB

protected void onANotB(int ai,
                       int bi)
Invoked for elements in a and not in b.


onBNotA

protected void onBNotA(int ai,
                       int bi)
Invoked for elements in b and not in a.


onMatch

protected void onMatch(int ai,
                       int bi)
Invoked for elements matching in a and b.


equals

protected boolean equals(Object x,
                         Object y)
Compares the two objects, using the comparator provided with the constructor, if any.


getLongestCommonSubsequences

public Integer[] getLongestCommonSubsequences()
Returns an array of the longest common subsequences.


toArray

protected static Integer[] toArray(TreeMap<Integer,Integer> map)
Converts the map (indexed by java.lang.Integers) into an array.


isNonzero

protected static boolean isNonzero(Integer i)
Returns whether the integer is not zero (including if it is not null).


isGreaterThan

protected boolean isGreaterThan(Integer index,
                                Integer val)
Returns whether the value in the map for the given index is greater than the given value.


isLessThan

protected boolean isLessThan(Integer index,
                             Integer val)
Returns whether the value in the map for the given index is less than the given value.


getLastValue

protected Integer getLastValue()
Returns the value for the greatest key in the map.


append

protected void append(Integer value)
Adds the given value to the "end" of the threshold map, that is, with the greatest index/key.


insert

protected Integer insert(Integer j,
                         Integer k)
Inserts the given values into the threshold map.



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