Java: read 2 files and compare line by line

Question

I'm trying to compare two files line by line. Let's say for example:

File1

a,b,c,d,12
e,f,g,h,20
h,g,t,y,30

File2

f,g,h,j,30
e,h,j,f,50
a,b,c,d,60
e,f,g,h,70

I want my output to be like:

a,b,c,d,12,50
e,f,g,h,20,70

I've written this code:

while ((line1 = bufferedFormattedReaderMaster.readLine()) != null) {

    temp1 = line1.substring(0, 7);
    temp3 = line1.substring(8, 10);

    while ((line2 = bufferedFormattedReaderAnalytical.readLine()) != null) {

        temp2 = line2.substring(0, 7);
        temp4 = line2.substring(8, 10);

        if (temp1.equals(temp2)) {

            System.out.println("OH YES");
            bufferedWriterFinalResults.write(temp1 + ","  +temp3 + "," + temp4);
            bufferedWriterFinalResults.newLine();
            numberOfFinalResults++;

        }   
    }
}

But my output is only:

a,b,c,d,12,50

and not the next line.

Gentle reminder that SO is not a place to get your homework done. — JVXR, Feb 05 '16 at 22:03
Hey, it's not for homework. I'm doing a research project with my professor and I've written this code a few days ago. I tried to debug the loops but it doesn't make sense. Is there something wrong with the way I defined my while loop? — Ravi Krishna, Feb 05 '16 at 22:05
Hint: You need to reset your inner loop to start reading at the beginning of the second file again once you have compared all lines with the first line of the first file. — Hulk, Feb 05 '16 at 22:07
quickest solution is just before second `while` line2 do read your file2... `BufferedReader bufferedFormattedReaderAnalytical = new BufferedReader(new FileReader("file-2.txt")); ` — MrSimpleMind, Feb 05 '16 at 22:12
and no, your output is wrong... you should get `a,b,c,d,12,60` .. 60 not 50. ;) — MrSimpleMind, Feb 05 '16 at 22:14

score 0 · Answer 1 · answered Feb 05 '16 at 22:11

The bufferedFormattedReaderMaster and bufferedFormattedReaderAnalytical can be read only one time. Brush up your skills on I/O. I did a simple list based conversion of your code. The code may not compile but this roughly what you have to implement. There are better ways as well.

List<String> bufferedFormattedReaderMasterList =new ArrayList<String>();
List<String> bufferedFormattedReaderAnalyticalList =new ArrayList<String>();
    while ((line1 = bufferedFormattedReaderMaster.readLine()) != null) {

                   bufferedFormattedReaderMasterList.add(line1 );
                }


    while ((line2 = bufferedFormattedReaderAnalytical.readLine()) != null) {

                   bufferedFormattedReaderAnalyticalList.add(line2);
                }



for(String line1:bufferedFormattedReaderMasterList) {

                    temp1 = line1.substring(0, 7);
                    temp3 = line1.substring(8, 10);

                    for(String line2:bufferedFormattedReaderAnalyticalList) {

                        temp2 = line2.substring(0, 7);
                        temp4 = line2.substring(8, 10);

                        if (temp1.equals(temp2)) {

                            System.out.println("OH YES");
                            bufferedWriterFinalResults.write(temp1 + ","  +temp3 + "," + temp4);
                            bufferedWriterFinalResults.newLine();
                            numberOfFinalResults++;

                        }   
                    }
                }

Java: read 2 files and compare line by line

1 Answers1