comparing 2 string array in java and print the same element from the both arrays

Question

below is my work so far i have used 2 csv files and made 2 different arrays which represents 2 csv file data now what i am want to do that is i want to compare that 2 arrays and print the same vlaues or elements which are same in both arrays this is where i am having difficulty

import java.util.Arrays;
import java.io.BufferedReader;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;

public class CSVReaderw {

public static void main(String[] args) {

    String csvFile1 = "/Users/Documents/AD.csv";
    String csvFile2 = "/Users/Desktop/database.csv";
    BufferedReader br = null;
    String line = "";
    String cvsSplitBy = ",";
    String[] ad = null;
    String[] database = null;

    try {

        br = new BufferedReader(new FileReader(csvFile1));
        while ((line = br.readLine()) != null) {

            // use comma as separator
             ad = line.split(cvsSplitBy);

            //System.out.println("AD [id= " + ad[2] +"]");

        }
        System.out.println("second file result starts here");
        br = new BufferedReader(new FileReader(csvFile2));
        while ((line = br.readLine()) != null) {

           database = line.split(cvsSplitBy);
           //System.out.println("ID =" + database[0]);
        }

        List<String> commonListLambda = Arrays.stream(database)
        .filter(x -> Arrays.asList(ad).contains(x))
        .collect(Collectors.toList());

        System.out.println(commonListLambda);
            // List<String> commonList = new ArrayList<>();
// 
//             for(int i = 0; i < ad.length; i++){
//                 if(Arrays.asList(databse).contains(ad[i]))
//                     commonList.add(ad[i]);
//                  }
//             
//             System.out.println(commonList);



    } catch (FileNotFoundException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    } finally {
        if (br != null) {
            try {
                br.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

}

}

Edit: see the updated code as we dicuessed here

in that questions they are only showing how to compare strings i want to comapre the values which is on the arrays and print the same values from arrays — newlearner
– newlearner, Commented Jul 29, 2017 at 16:50
if(ad[i] == database[j]) You are comparing string that you get from the files. It is exactly the same solution. — Jorge Campos
– Jorge Campos, Commented Jul 29, 2017 at 16:51

fg78nc · Accepted Answer · 2017-07-29 20:12:30Z

1

The problem is that you are rewriting again your array, instead of adding data to it.

while ((line = br.readLine()) != null) {
           database = line.split(cvsSplitBy);

General logic is wrong, you need to compare cell in one file to the cell in other file.

Please see suggested solution, I tried to make code self-explanatory.

public class CSVReaderw {

    public static void main(String[] args) {

        String adDotCsv = "/Users/Documents/AD.csv";
        String databaseDotCsv = "/Users/Desktop/database.csv";
        String line = "";
        String cvsSplitBy = ",";
        BufferedReader br = null;
        List<String> databaseList = new ArrayList<>();
        List<String[]> adList = new ArrayList<>();

        try {
            br = new BufferedReader(new FileReader(databaseDotCsv));

            while ((line = br.readLine()) != null) {
                databaseList.addAll(Arrays.asList(line.split(cvsSplitBy)));
            }

            br = new BufferedReader(new FileReader(adDotCsv));

            line = "";
            while ((line = br.readLine()) != null) {
                adList.add(line.split(cvsSplitBy));
            }

            List<String[]> commonList = new ArrayList<>();

            String cellCInAdFile = null;

            for (String[] rowInAdList : adList) {
                cellCInAdFile = Arrays.toString(rowInAdList).split(",")[2].trim();

                for (String cellAinDatabaseFile : databaseList) {
                    if (cellCInAdFile.equals(cellAinDatabaseFile.trim())) {
                        commonList.add(rowInAdList);
                    }
                }
            }

            for (String[] rowInCommonList : commonList) {
                System.out.println(Arrays.asList(rowInCommonList));
            }

        } catch (IOException ex) {
            ex.printStackTrace();
        }
    }
}

edited Jul 29, 2017 at 20:12

answered Jul 29, 2017 at 17:10

fg78nc

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10 Comments

newlearner Over a year ago

so i have to replace my inner for loop right?? @fg78nc

fg78nc Over a year ago

I did not study attention to your code. This is complete solution which will compare two arrays and return List of common elements. Let me know if you need additional help

newlearner Over a year ago

for(int i = 0; i < ad.length; i++) { for(int j = 0; j < database.length; ++j) { if(!Arrays.asList(ad).contains(database[i])) commonList.add(database[i]); System.out.println(commonList); //value is in both arrays } } this what i did but it's not working gives me cannot find symbol on commonList

fg78nc Over a year ago

You don't need outer loop, only one loop is enough.

fg78nc Over a year ago

import java.util.stream.Collectors;

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