CODEWITHSUNDEEP
javafilefilereader
nawara
nawara

Reputation: 1167

Copy lines from a File to another

I need to copy a line from a file to another depending on condition this is my code 

     import org.apache.commons.io.FileUtils;

     public class FileCopy {

public static void main(String args[]) throws IOException { 

    File source = \\
    File fileToCopyFrom \\
    File target :\\
    if (!target.exists()) {
        target.createNewFile();
    }

    PrintStream fstream =new PrintStream(target);
    BufferedReader brSource = new BufferedReader(new FileReader(source));
    BufferedReader brFileToCopyFrom = new BufferedReader(new FileReader(fileToCopyFrom));

    String lineSource;
    String lineToCopy;

    while((lineSource = brSource.readLine()) != null) {

          while ((lineToCopy=brFileToCopyFrom.readLine())!=null) {
    if (lineToCopy.contains(lineSource.substring(lineSource.indexOf("_")+1, lineSource.indexOf(".")-1)))
                fstream.println(lineToCopy);    
            }

        }
}}

but it copy only the first line where is the error?

Upvotes: 1

Views: 5421

Answers (3)

user902383
user902383

Reputation: 8640

you create your stream, you read all enntries from your stream, for first line, but when you want to do this for second line brFileToCopyFrom is empty (you already took everything from it when you were checking your first line.

so what you could do is move creating your brFileToCopyFrom to the loop,

while((lineSource = brSource.readLine()) != null) {
BufferedReader brFileToCopyFrom = new BufferedReader(new FileReader(fileToCopyFrom));

...

that should works

Upvotes: 0

Eduardo
Eduardo

Reputation: 697

Only the first is copied because in the second iteration of the first while the brFileToCopyFrom is reached the end of file.

You need to open the BufferedReader brFileToCopy inside the first while (example 1) or use a mark/reset feature (example 2).

Example 1:

while ((lineSource = brSource.readLine()) != null) {

        BufferedReader brFileToCopyFrom = new BufferedReader(new FileReader(fileToCopyFrom));

        while ((lineToCopy = brFileToCopyFrom.readLine()) != null) {
            ...
        }

    }
}

Example 2:

brFileToCopyFrom.mark(1024); // number of characters to be read while preserving the mark

while ((lineSource = brSource.readLine()) != null) {

        brFileToCopyFrom.reset();

        while ((lineToCopy = brFileToCopyFrom.readLine()) != null) {
            ...
        }

    }
}

Upvotes: 1

NPKR
NPKR

Reputation: 5496

I suggest to use commons-io.jar. In this FileUtils class lot of methods to do File operation like copy, move and remove.

EDIT

try with below if conndition which contains break.

while ((lineSource = brSource.readLine()) != null) {

            while ((lineToCopy = brFileToCopyFrom.readLine()) != null) {
                if (lineToCopy.contains(lineSource.substring(
                        lineSource.indexOf("_") + 1,
                        lineSource.indexOf(".") - 1))) {
                    fstream.println(lineToCopy);
                    break;
                }
            }

        }

Upvotes: 1

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