Package jdiff

Class DiffMyers

  • public class DiffMyers
extends java.lang.Object
    A class to compare vectors of objects. The result of comparison is a list of change objects which form an edit script. The objects compared are traditionally lines of text from two files. Comparison options such as "ignore whitespace" are implemented by modifying the equals and hashcode methods for the objects compared.

    The basic algorithm is described in:
    "An O(ND) Difference Algorithm and its Variations", Eugene Myers, Algorithmica Vol. 1 No. 2, 1986, p 251.

    This class outputs different results from GNU diff 1.15 on some inputs. Our results are actually better (smaller change list, smaller total size of changes), but it would be nice to know why. Perhaps there is a memory overwrite bug in GNU diff 1.15.

    • Nested Class Summary

      Nested Classes 
      Modifier and Type Class Description
      static class  DiffMyers.change
      The result of comparison is an "edit script": a chain of change objects.

    • Field Summary

      Fields 
      Modifier and Type Field Description
      boolean heuristic
      When set to true, the comparison uses a heuristic to speed it up.
      boolean no_discards
      When set to true, the algorithm returns a guarranteed minimal set of changes.

    • Constructor Summary

      Constructors 
      Constructor Description
      DiffMyers​(java.lang.Object[] a, java.lang.Object[] b)
      Prepare to find differences between two arrays.

    • Method Summary

      All Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      DiffMyers.change diff_2​(boolean reverse)  

      • Methods inherited from class java.lang.Object

        clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

    • Field Detail

      • heuristic

        public boolean heuristic
        When set to true, the comparison uses a heuristic to speed it up. With this heuristic, for files with a constant small density of changes, the algorithm is linear in the file size.

      • no_discards

        public boolean no_discards
        When set to true, the algorithm returns a guarranteed minimal set of changes. This makes things slower, sometimes much slower.

    • Constructor Detail

      • DiffMyers

        public DiffMyers​(java.lang.Object[] a,
                 java.lang.Object[] b)
        Prepare to find differences between two arrays. Each element of the arrays is translated to an "equivalence number" based on the result of equals. The original Object arrays are no longer needed for computing the differences. They will be needed again later to print the results of the comparison as an edit script, if desired.