Java - Two Files comparison with hash and array match

Question

I am trying to compare two files based on md5 hash and array match to have performance efficient process .i.e. if both byte values are matched then both files content are same else it moves to array match to find out the difference between two file. Problem what I am facing here is byte values are different for same files so it is moving to array match which is not necessary in this case.

Java Code:

import java.io.BufferedReader;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.io.InputStream;
import java.util.Date;
import java.util.concurrent.TimeUnit;
import java.security.DigestInputStream;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

public class CompareTwoFiles {
    static int count1 = 0 ;
    static int count2 = 0 ;

    static String arrayLines1[] = new String[countLines("\\Files_Comparison\\File11.txt")];
    static String arrayLines2[] = new String[countLines("\\Files_Comparison\\File12.txt")];

    public static void main(String args[]) throws Throwable{  
        long lStartTime = new Date().getTime();
        System.out.println("File1 count=" + countLines("\\Files_Comparison\\File11.txt"));
        System.out.println("File2 count=" + countLines("\\Files_Comparison\\File12.txt"));
        MessageDigest md_1 = MessageDigest.getInstance("MD5");
        MessageDigest md_2 = MessageDigest.getInstance("MD5");
        InputStream is_1 = new FileInputStream("\\Files_Comparison\\File11.txt");
        InputStream is_2 = new FileInputStream("\\Files_Comparison\\File12.txt");
        try {
          is_1 = new DigestInputStream(is_1, md_1);
          is_2 = new DigestInputStream(is_2, md_2);
        }
        finally {
          is_1.close();
          is_2.close();
        }
        byte[] digest_1 = md_1.digest();
        byte[] digest_2 = md_2.digest();
        System.out.println(digest_1);
        System.out.println(digest_2);
        if (digest_1.equals(digest_2)) {
            System.out.println("File Comparison Process Completed");
            System.out.println("Both files are same");
        }
        else 
        {
        findDifference("\\Files_Comparison\\File11.txt","\\Files_Comparison\\File12.txt");
        displayRecords();
        System.out.println("File Comparison Process Completed");
        }
        long lEndTime = new Date().getTime();
        long difference = lEndTime - lStartTime; 
        String hms = String.format("%02d:%02d:%02d", TimeUnit.MILLISECONDS.toHours(difference),
                TimeUnit.MILLISECONDS.toMinutes(difference) - TimeUnit.HOURS.toMinutes(TimeUnit.MILLISECONDS.toHours(difference)),
                TimeUnit.MILLISECONDS.toSeconds(difference) - TimeUnit.MINUTES.toSeconds(TimeUnit.MILLISECONDS.toMinutes(difference)));
        System.out.println(hms);
    }

    public static int countLines(String File){

        int lineCount = 0;
        try {
           BufferedReader br = new BufferedReader(new FileReader(File));
           while ((br.readLine()) != null) {
               lineCount++;
           }

       } catch (FileNotFoundException e) {
           e.printStackTrace();
       } catch (IOException e) {
           e.printStackTrace();
       }
           return lineCount;
    }

    public static void findDifference(String File1, String File2){
        String contents1 = null;  
        String contents2 = null; 
        try  
        {  
            FileReader file1 = new FileReader(File1);  
            FileReader file2 = new FileReader(File2);
            BufferedReader buf1 = new BufferedReader(file1); 
            BufferedReader buf2 = new BufferedReader(file2);

           while ((contents1 = buf1.readLine()) != null)  
            {  
               arrayLines1[count1] = contents1 ;
               count1++;
            }  

           while ((contents2 = buf2.readLine()) != null)  
            {  
               arrayLines2[count2] = contents2 ;
               count2++;
            }
       }catch (Exception e){
           e.printStackTrace();
       }
}





    public static void displayRecords() { 

        for (int i = 0 ; i < arrayLines1.length && i < arrayLines2.length; i++) 
        {    
            String a = arrayLines1[i];  
            String b = arrayLines2[i];  

            if(!a.contains(b)) {  
                   System.out.println(a);  
            }  
        }
    }

}

score 0 · Answer 1 · edited May 23 '17 at 12:13

0

Probably you took your solution from this post, but forgot to read this line:

 /* Read decorated stream (dis) to EOF as normal... */

You have to read from the DigestInputStream's until the whole file is read. If you immediately close the streams after opening, they will see nothing at all from the file and will both return the same Digest for "no Byte at all".

edited May 23 '17 at 12:13

Community

1
1

answered Nov 11 '16 at 13:42

Thomas Philipp

261
1
5

score 0 · Answer 2 · answered Nov 11 '16 at 14:09

0

Thanks for you response. The post which you have shared was really helpful. I am able to get the expected solution by using below code:

String checksum = DigestUtils.md5Hex(new FileInputStream(filePath));

answered Nov 11 '16 at 14:09

jay

43
1
9

Java - Two Files comparison with hash and array match

2 Answers2