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How to merge two csv files with same header columns into another csv file using java

How can I concatenate two arrays in Java?How do I call one constructor from another in Java?How do I create a Java string from the contents of a file?How do I create a file and write to it in Java?How to avoid Java code in JSP files?How to sort CSV file by header?Merging a bunch of csv files into one with headersExtract and merge columns in a CSVcompare a set of strings from one csv file in another csv file using Unix Shell scriptScript to map columns in two csv files

0

csv file 1:

a|b|c
a|a|a
b|b|b

csv file 2:

a|b|c
c|c|c
d|d|d

output csv file:

a|b|c
a|a|a
b|b|b
c|c|c
d|d|d

here's my code i tried to merge but the header is repeating twice :
and when it comes to merging two files into single alternate csv file then also iam facing the same issue as the above the header columns gets repeated everytime what am i supposed to do to ignore it.
here's my code below

 public static void main(String[] args) throws IOException 
{ 
 // PrintWriter object for file3.txt 
 PrintWriter pw = new PrintWriter("file3.txt"); 

 // BufferedReader object for file1.txt 
 BufferedReader br1 = new BufferedReader(new FileReader("file1.txt")); 
 BufferedReader br2 = new BufferedReader(new FileReader("file2.txt")); 


 String line1 = br1.readLine(); 
 String line2 = br2.readLine(); 

 // loop to copy lines of 
 // file1.txt and file2.txt 
 // to file3.txt alternatively 
 while (line1 != null || line2 !=null) 
 
 if(line1 != null) 
 
 pw.println(line1); 
 line1 = br1.readLine(); 
 

 if(line2 != null) 
 
 pw.println(line2); 
 line2 = br2.readLine(); 
 
 

 pw.flush(); 

 // closing resources 
 br1.close(); 
 br2.close(); 
 pw.close(); 

howw to skip the header column in the output file

java performance csv

share|improve this question

edited 2 days ago

pragadeeshwaran venkatachalam

asked 2 days ago

pragadeeshwaran venkatachalampragadeeshwaran venkatachalam

34

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  So you want a file with only the unique lines of all input files?
  
  – Robert Kock
  2 days ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Are the input files sorted? Is the order of the lines in the output file important?
  
  – Robert Kock
  2 days ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  no the order is not important but the data should not be skipped if they have duplicates they should not be skipped
  
  – pragadeeshwaran venkatachalam
  2 days ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  i have added another code with two files merged to single file its also getting the same issue how to ignore the header column
  
  – pragadeeshwaran venkatachalam
  2 days ago
  

  
  
  
  

add a comment | 

0

csv file 1:

a|b|c
a|a|a
b|b|b

csv file 2:

a|b|c
c|c|c
d|d|d

output csv file:

a|b|c
a|a|a
b|b|b
c|c|c
d|d|d

here's my code i tried to merge but the header is repeating twice :
and when it comes to merging two files into single alternate csv file then also iam facing the same issue as the above the header columns gets repeated everytime what am i supposed to do to ignore it.
here's my code below

 public static void main(String[] args) throws IOException 
{ 
 // PrintWriter object for file3.txt 
 PrintWriter pw = new PrintWriter("file3.txt"); 

 // BufferedReader object for file1.txt 
 BufferedReader br1 = new BufferedReader(new FileReader("file1.txt")); 
 BufferedReader br2 = new BufferedReader(new FileReader("file2.txt")); 


 String line1 = br1.readLine(); 
 String line2 = br2.readLine(); 

 // loop to copy lines of 
 // file1.txt and file2.txt 
 // to file3.txt alternatively 
 while (line1 != null || line2 !=null) 
 
 if(line1 != null) 
 
 pw.println(line1); 
 line1 = br1.readLine(); 
 

 if(line2 != null) 
 
 pw.println(line2); 
 line2 = br2.readLine(); 
 
 

 pw.flush(); 

 // closing resources 
 br1.close(); 
 br2.close(); 
 pw.close(); 

howw to skip the header column in the output file

java performance csv

share|improve this question

edited 2 days ago

pragadeeshwaran venkatachalam

asked 2 days ago

pragadeeshwaran venkatachalampragadeeshwaran venkatachalam

34

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  So you want a file with only the unique lines of all input files?
  
  – Robert Kock
  2 days ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Are the input files sorted? Is the order of the lines in the output file important?
  
  – Robert Kock
  2 days ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  no the order is not important but the data should not be skipped if they have duplicates they should not be skipped
  
  – pragadeeshwaran venkatachalam
  2 days ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  i have added another code with two files merged to single file its also getting the same issue how to ignore the header column
  
  – pragadeeshwaran venkatachalam
  2 days ago
  

  
  
  
  

add a comment | 

csv file 1:

a|b|c
a|a|a
b|b|b

csv file 2:

a|b|c
c|c|c
d|d|d

output csv file:

a|b|c
a|a|a
b|b|b
c|c|c
d|d|d

here's my code i tried to merge but the header is repeating twice :
and when it comes to merging two files into single alternate csv file then also iam facing the same issue as the above the header columns gets repeated everytime what am i supposed to do to ignore it.
here's my code below

 public static void main(String[] args) throws IOException 
{ 
 // PrintWriter object for file3.txt 
 PrintWriter pw = new PrintWriter("file3.txt"); 

 // BufferedReader object for file1.txt 
 BufferedReader br1 = new BufferedReader(new FileReader("file1.txt")); 
 BufferedReader br2 = new BufferedReader(new FileReader("file2.txt")); 


 String line1 = br1.readLine(); 
 String line2 = br2.readLine(); 

 // loop to copy lines of 
 // file1.txt and file2.txt 
 // to file3.txt alternatively 
 while (line1 != null || line2 !=null) 
 
 if(line1 != null) 
 
 pw.println(line1); 
 line1 = br1.readLine(); 
 

 if(line2 != null) 
 
 pw.println(line2); 
 line2 = br2.readLine(); 
 
 

 pw.flush(); 

 // closing resources 
 br1.close(); 
 br2.close(); 
 pw.close(); 

howw to skip the header column in the output file

java performance csv

share|improve this question

edited 2 days ago

pragadeeshwaran venkatachalam

asked 2 days ago

pragadeeshwaran venkatachalampragadeeshwaran venkatachalam

34

a|b|c
a|a|a
b|b|b

a|b|c
c|c|c
d|d|d

a|b|c
a|a|a
b|b|b
c|c|c
d|d|d

 public static void main(String[] args) throws IOException 
{ 
 // PrintWriter object for file3.txt 
 PrintWriter pw = new PrintWriter("file3.txt"); 

 // BufferedReader object for file1.txt 
 BufferedReader br1 = new BufferedReader(new FileReader("file1.txt")); 
 BufferedReader br2 = new BufferedReader(new FileReader("file2.txt")); 


 String line1 = br1.readLine(); 
 String line2 = br2.readLine(); 

 // loop to copy lines of 
 // file1.txt and file2.txt 
 // to file3.txt alternatively 
 while (line1 != null || line2 !=null) 
 
 if(line1 != null) 
 
 pw.println(line1); 
 line1 = br1.readLine(); 
 

 if(line2 != null) 
 
 pw.println(line2); 
 line2 = br2.readLine(); 
 
 

 pw.flush(); 

 // closing resources 
 br1.close(); 
 br2.close(); 
 pw.close(); 

share|improve this question

edited 2 days ago

pragadeeshwaran venkatachalam

asked 2 days ago

pragadeeshwaran venkatachalampragadeeshwaran venkatachalam

34

share|improve this question

edited 2 days ago

pragadeeshwaran venkatachalam

asked 2 days ago

pragadeeshwaran venkatachalampragadeeshwaran venkatachalam

34

asked 2 days ago

pragadeeshwaran venkatachalampragadeeshwaran venkatachalam

34

asked 2 days ago

pragadeeshwaran venkatachalampragadeeshwaran venkatachalam

34

1 Answer
1

active

oldest

votes

0

Just skip the first lines of second and subsequent CSV files:

 for (int i = 0; i < fileNames.length; i++) 
 System.out.println("Reading from " + fileNames[i]); 

 File f = new File(dir, fileNames[i]);

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

 String line = br.readLine();
 if (i > 0) 
 line = br.readLine(); //just skip the first line

 while (line != null) 
 pw.println(line); 
 line = br.readLine(); 
 

 pw.flush(); 
 

share|improve this answer

edited 2 days ago

Jaja

516

answered 2 days ago

Pavel SmirnovPavel Smirnov

1,177214

add a comment | 

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0

Just skip the first lines of second and subsequent CSV files:

 for (int i = 0; i < fileNames.length; i++) 
 System.out.println("Reading from " + fileNames[i]); 

 File f = new File(dir, fileNames[i]);

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

 String line = br.readLine();
 if (i > 0) 
 line = br.readLine(); //just skip the first line

 while (line != null) 
 pw.println(line); 
 line = br.readLine(); 
 

 pw.flush(); 
 

share|improve this answer

edited 2 days ago

Jaja

516

answered 2 days ago

Pavel SmirnovPavel Smirnov

1,177214

add a comment | 

0

Just skip the first lines of second and subsequent CSV files:

 for (int i = 0; i < fileNames.length; i++) 
 System.out.println("Reading from " + fileNames[i]); 

 File f = new File(dir, fileNames[i]);

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

 String line = br.readLine();
 if (i > 0) 
 line = br.readLine(); //just skip the first line

 while (line != null) 
 pw.println(line); 
 line = br.readLine(); 
 

 pw.flush(); 
 

share|improve this answer

edited 2 days ago

Jaja

516

answered 2 days ago

Pavel SmirnovPavel Smirnov

1,177214

add a comment | 

Just skip the first lines of second and subsequent CSV files:

 for (int i = 0; i < fileNames.length; i++) 
 System.out.println("Reading from " + fileNames[i]); 

 File f = new File(dir, fileNames[i]);

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

 String line = br.readLine();
 if (i > 0) 
 line = br.readLine(); //just skip the first line

 while (line != null) 
 pw.println(line); 
 line = br.readLine(); 
 

 pw.flush(); 
 

share|improve this answer

edited 2 days ago

Jaja

516

answered 2 days ago

Pavel SmirnovPavel Smirnov

1,177214

 for (int i = 0; i < fileNames.length; i++) 
 System.out.println("Reading from " + fileNames[i]); 

 File f = new File(dir, fileNames[i]);

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

 String line = br.readLine();
 if (i > 0) 
 line = br.readLine(); //just skip the first line

 while (line != null) 
 pw.println(line); 
 line = br.readLine(); 
 

 pw.flush(); 
 

share|improve this answer

edited 2 days ago

Jaja

516

answered 2 days ago

Pavel SmirnovPavel Smirnov

1,177214

edited 2 days ago

Jaja

516

edited 2 days ago

Jaja

516

answered 2 days ago

Pavel SmirnovPavel Smirnov

1,177214

answered 2 days ago

Pavel SmirnovPavel Smirnov

1,177214