How to make a multiline file into a single line file delimited with a control character

Question

I'm trying to parse a file like this:

textfile.txt

_=1406048396605
bh=1244
bw=1711
c=24
c19=DashboardScreen
c2=2014-07-22T10:00:00-0700
c4=64144090210294
c40=3#undefined#0#0#a=-2#512#-1#0
c41=14060470498427c3e4ed
c46=Green|firefox|Firefox|30|macx|Mac OS X
c5=NONFFA
c6=HGKhjgj
c7=OFF_SEASON|h:PARTIAL|
ch=YHtgsfT
g=https://google.hello.com
h5=77dbf90c-5794-4a40-b1ab-fe1c82440c68-1406048401346
k=true
p=Shockwave Flash;QuickTime Plug-in 7.7.3;Default Browser Helper;SharePoint Browser Plug-in;Java Applet Plug-in;Silverlight Plug-In
pageName=DashboardScreen - Loading...
pageType= 
pe=lnk_o
pev2=pageDetail
s=2432x1520
server=1.1 pqalmttws301.ie.google.net:81
t=22/06/2014 10:00:00 2 420
v12=3468337910
v4=0
v9=dat=279333:279364:375870:743798:744035:743802:744033:743805:783950:783797:783949:784088
vid=29E364C5051D2894-400001468000F0EE

into something like this:

_=1406048396605<CONTROL_CHARACTER_HERE>bh=1244<CONTROL_CHARACTER_HERE>bw=1711<CONTROL_CHARACTER_HERE>c=24<CONTROL_CHARACTER_HERE>c19=DashboardScreenc2=2014-07-22T10:00:00-0700.....etc

So I'm basically taking a multiline file and making it into a single line file delimiting each field with a CONTROL_CHARACTER.

This is what I currently have:

private String putIntoExpectedFormat() { 

    File f1 = new File("InputFile.txt");
    File f2 = new File("OutputFile.txt"); 

    InputStream in = new FileInputStream(f1);
    OutputStream out = new FileOutputStream(f2); 

    StringBuilder sb = new StringBuilder();

    byte[] buf = new byte[1024];
    int len;

    while( (len=in.read(buf)) > 0) {



        out.write(buf,0,len);
    }

    in.close();
    out.close();

}

I'm not even sure if I'm doing this right. Does anybody know how to do this?

Why not just read file line by line and write these lines to other file with `` before each line except first one? — Pshemo, Jul 22 '14 at 17:46
http://stackoverflow.com/questions/5868369/how-to-read-a-large-text-file-line-by-line-using-java — Pshemo, Jul 22 '14 at 17:47

Braj · Answer 1 · 2014-07-22T17:52:38.073

Since its a text file hence you have to use Reader classes for reading character streams. For better performance use BufferedReader

Reads text from a character-input stream, buffering characters so as to provide for the efficient reading of characters, arrays, and lines.

You can use Java 7 - The try-with-resources Statement

sample code:

try (BufferedReader reader = new BufferedReader(new FileReader(
        new File("InputFile.txt")));
     BufferedWriter writer = new BufferedWriter(new FileWriter(
        new File("OutputFile.txt")))) {
    String line = null;
    while ((line = reader.readLine()) != null) {
        writer.write(line);
        // write you <CONTROL_CHARACTER_HERE> as well
    }
}

but I don't want to remove my thanks. You comments are valid and there is no need to remove it because as I mentioned in my last comment that I have edited it. — Braj, Jul 22 '14 at 17:55

score 1 · Accepted Answer · answered Jul 22 '14 at 17:51

Easiest way is to use Scanner and PrintWriter:

    Scanner in = null;
    PrintWriter out = null;
    try {
        // init input, output
        in = new Scanner(new File("InputFile.txt"));
        out = new PrintWriter(new File("OutputFile.txt"));
        // read input file line by line
        while (in.hasNextLine()) {
            out.print(in.nextLine());
            if (in.hasNextLine()) {
                out.print("<CONTROL_CHARACTER>");
            }
        }
    } finally {
        // close input, output
        if (in != null) {
            in.close();
        }
        if (out != null) {
            out.close();
        }
    }

score 1 · Answer 3 · answered Jul 22 '14 at 17:56

Here are three pieces of code which will read the file, replace all newlines with you <CONTROL_CHARACTER> and then write the file.

Read the file:

public static String readFile(String filePath) {
    String entireFile = "";

    File file = new File(filePath);

    if (file.exists()) {
        BufferedReader br;
        try {
            br = new BufferedReader(new FileReader(file));

            String line;
            while ((line = br.readLine()) != null) {
                entireFile += line + "\n";
            }

            br.close();

        } catch (FileNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    } else {
        System.err.println("File " + filePath + " does not exist!");
    }

    return entireFile;
}

Change newlines to <Control-Character>:

String text = readFile("Path/To/file.txt");
text = text.replace("\n", <Control-Character-Here>);

Write the file:

writeToFile("Path/to/newfile.txt", text);

Here is the method writeToFile()

public static void writeToFile(String filePath, String toWrite) {
    File file  = new File(filePath);
    if (!file.exists()) {
        try {
            file.createNewFile();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            System.err.println(filePath + " does not exist. Failed to create new file");
        }
    }

    try {
        PrintWriter out = new PrintWriter(new BufferedWriter(new FileWriter(filePath, true)));
        out.println(toWrite);
        out.close();
    } catch (IOException e) {
        System.err.println("Could not write to file: " + filePath);
    }
}

score 0 · Answer 4 · answered Jul 23 '14 at 05:06

Used Guava 17.0.
Useful for small size files. Not tested for large and very large files.I think as per the question is considered the expected input file is is small size.
Here we are not processing each lines, so reading line by line is not required.

One more Way using Guava IO libraries

    public static void main(String[] args) {
        try {
            String content = Files.toString(new File("/home/chandrayya/InputFile.txt"), Charsets.UTF_8);//Change charset accordingly
            content = content.replaceAll("\r\n"/*\r\n windows format, \n UNIX/OSX format \r old mac format*/, "<C>"/*C is control character.*/);
            Files.write(content, new File("/home/chandrayya/OutputFile.txt.txt"), Charsets.UTF_8 );
        } catch( IOException e ) {
            e.printStackTrace();
        }
    }

How to make a multiline file into a single line file delimited with a control character

4 Answers4

One more Way using Guava IO libraries