Class SequencesComparator<T>
The two sequences can hold any object type, as only the equals
method is used to compare the elements of the sequences. It is guaranteed
that the comparisons will always be done as o1.equals(o2)
where
o1
belongs to the first sequence and o2
belongs to
the second sequence. This can be important if subclassing is used for some
elements in the first sequence and the equals
method is
specialized.
Comparison can be seen from two points of view: either as giving the smallest
modification allowing to transform the first sequence into the second one, or
as giving the longest sequence which is a subsequence of both initial
sequences. The equals
method is used to compare objects, so any
object can be put into sequences. Modifications include deleting, inserting
or keeping one object, starting from the beginning of the first sequence.
This class implements the comparison algorithm, which is the very efficient
algorithm from Eugene W. Myers
An O(ND) Difference Algorithm and Its Variations. This algorithm produces
the shortest possible
edit script
containing all the
commands
needed to transform the first sequence into the second one.
- Since:
- 4.0
- See Also:
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Nested Class Summary
Nested ClassesModifier and TypeClassDescriptionprivate static class
This class is a simple placeholder to hold the end part of a path under construction in aSequencesComparator
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Field Summary
Fields -
Constructor Summary
Constructors -
Method Summary
Modifier and TypeMethodDescriptionprivate void
buildScript
(int start1, int end1, int start2, int end2, EditScript<T> script) Build an edit script.private SequencesComparator.Snake
buildSnake
(int start, int diag, int end1, int end2) Build a snake.private SequencesComparator.Snake
getMiddleSnake
(int start1, int end1, int start2, int end2) Get the middle snake corresponding to two subsequences of the main sequences.Get theEditScript
object.
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Field Details
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sequence1
First sequence. -
sequence2
Second sequence. -
equator
The equator used for testing object equality. -
vDown
private final int[] vDownTemporary variables. -
vUp
private final int[] vUp
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Constructor Details
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SequencesComparator
Simple constructor.Creates a new instance of SequencesComparator using a
DefaultEquator
.It is guaranteed that the comparisons will always be done as
o1.equals(o2)
whereo1
belongs to the first sequence ando2
belongs to the second sequence. This can be important if subclassing is used for some elements in the first sequence and theequals
method is specialized.- Parameters:
sequence1
- first sequence to be comparedsequence2
- second sequence to be compared
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SequencesComparator
Simple constructor.Creates a new instance of SequencesComparator with a custom
Equator
.It is guaranteed that the comparisons will always be done as
Equator.equate(o1, o2)
whereo1
belongs to the first sequence ando2
belongs to the second sequence.- Parameters:
sequence1
- first sequence to be comparedsequence2
- second sequence to be comparedequator
- the equator to use for testing object equality
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Method Details
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getScript
Get theEditScript
object.It is guaranteed that the objects embedded in the
insert commands
come from the second sequence and that the objects embedded in either thedelete commands
orkeep commands
come from the first sequence. This can be important if subclassing is used for some elements in the first sequence and theequals
method is specialized.- Returns:
- the edit script resulting from the comparison of the two sequences
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buildSnake
Build a snake.- Parameters:
start
- the value of the start of the snakediag
- the value of the diagonal of the snakeend1
- the value of the end of the first sequence to be comparedend2
- the value of the end of the second sequence to be compared- Returns:
- the snake built
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getMiddleSnake
Get the middle snake corresponding to two subsequences of the main sequences.The snake is found using the MYERS Algorithm (this algorithms has also been implemented in the GNU diff program). This algorithm is explained in Eugene Myers article: An O(ND) Difference Algorithm and Its Variations.
- Parameters:
start1
- the begin of the first sequence to be comparedend1
- the end of the first sequence to be comparedstart2
- the begin of the second sequence to be comparedend2
- the end of the second sequence to be compared- Returns:
- the middle snake
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buildScript
Build an edit script.- Parameters:
start1
- the begin of the first sequence to be comparedend1
- the end of the first sequence to be comparedstart2
- the begin of the second sequence to be comparedend2
- the end of the second sequence to be comparedscript
- the edited script
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