I made a Diff tool for Java files


It's a continuation of the one I wrote earlier (or yesterday).

Click here for the relevant article!

I wrote a Java source analysis tool in Java ... https://qiita.com/banana5388/items/cd8a549d1885aa6dd039

In the comment of the previous article, you pointed out that "let's start with something simple", so I started by simply getting the number of difference steps between the two source codes.

(Don't say redevelopment of the wheels !!!!!! It was fun to make something !!!) </ font>

So the input and output of what I will create this time is like this.

INPUT :Absolute path of comparison source and comparison destination
OUTPUT:Number of steps with different code


What I was thinking about for the time being is something like this.

  1. Analyze the obtained code for each of the comparison source and comparison destination character by character.
  2. If different characters appear between the comparison source and the comparison destination, stop the comparison source at the current character position and move the comparison destination character to the next character analysis.
  3. If the same character as the comparison source appears at the comparison destination, the character analysis of the comparison source is restarted.
  4. If a line feed character appears at the comparison destination while the comparison source character analysis is stopped, add 1 difference step.
  5. Continue the process of [2. --4] until the characters of the comparison source or comparison destination are completed.
  6. Output how many lines are different as a result of analysis

For the time being, I implemented this as it is.

The implementation of the main part looks like this.


     *Compares two codes and returns the number of matching lines
     * @param origCode Comparison source code (stored in a list for each line)
     * @param destCode Comparison code (stored in a list for each line)
     * @return Number of matching lines for comparison
    public static int countCodeDiff(List<String> origCode, List<String> destCode) {

        int cnt = 0;

        //Generating iterators for strings

        //The method "getNotIncludeIgnoreCode" is based on the line-by-line code information stored in the list.
        //Erase half-width spaces, full-width spaces, tab characters, and line feed characters, and add a line feed character at the end.
        //It is a method that finally returns as one character string (String type).
        StringCharacterIterator origCodeIterator =  new StringCharacterIterator(getNotIncludeIgnoreCode(origCode));
        StringCharacterIterator destCodeIterator =  new StringCharacterIterator(getNotIncludeIgnoreCode(destCode));

        //Execute until the character of either the comparison source or the comparison destination ends
        while (origCodeIterator.current() != StringCharacterIterator.DONE &&
                destCodeIterator.current() != StringCharacterIterator.DONE) {

            //Increase the count when different code characters are included in the comparison source and comparison destination, and the comparison destination has a line break first.
            if (origCodeIterator.current() == destCodeIterator.current()) {
            } else {
                if (destCodeIterator.current() == '\n') {

        return cnt;

Um, isn't it a good feeling? ??


First test

I prepared the text for testing.





It's not a java file at all, but for the time being, it's for testing, so is this okay? Well, the output is. .. ..

> Number of different lines: 0

Yeah, it looks good.

Second test

Another test





Well, the output is. .. ..

> Difference Code Line Count:3

This looks good too.


For the time being, I am satisfied because it is moving according to the specifications.

Rather, the specifications are rather loose ... I would like to reimplement it so that it can be used.

The source is open to the public

Yes. https://github.com/satodaiki/DiffTool

Change log

2018/12/2 First edition 2018/12/3 There was some error in the source, so I fixed it.

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