java.lang.Object
- dk.netarkivet.testutils.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

Fields
Modifier and Type	Field	Description
`protected Object[]`	`a`	The source array, AKA the "from" values.
`protected Object[]`	`b`	The target array, AKA the "to" values.
`protected List`	`diffs`	The list of differences, as `Difference` instances.

Constructor Summary

Constructors
Constructor	Description
`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.
`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.

Method Summary

All Methods Static Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`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`	`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 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 Object[] a
```
    The source array, AKA the "from" values.
  - b
```
protected Object[] b
```
    The target array, AKA the "to" values.
  - diffs
```
protected List 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 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 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.

Class Diff

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

a

b

diffs

Constructor Detail

Diff

Diff

Diff

Diff

Method Detail

diff

traverseSequences

callFinishedA

callFinishedB

finishedA

finishedB

onANotB

onBNotA

onMatch

equals

getLongestCommonSubsequences

toArray

isNonzero

isGreaterThan

isLessThan

getLastValue

append

insert