BufferedReader: read multiple lines into a single string

Question

I\'m reading numbers from a txt file using BufferedReader for analysis. The way I\'m going about this now is- reading a line using .readline, splitting this string into an a

Answer 1

You have a file containing doubles. Looks like you have more than one number per line, and may have multiple lines.

Simplest thing to do is read lines in a while loop.

You could return null from your ReadBigStringIn method when last line is reached and terminate your loop there.

But more normal would be to create and use the reader in one method. Perhaps you could change to a method which reads the file and returns an array or list of doubles.

BTW, could you simply split your strings by whitespace?

Reading a whole file into a single String may suit your particular case, but be aware that it could cause a memory explosion if your file was very large. Streaming approach is generally safer for such i/o.

Answer 2

If you just want to read the entirety of a file into a string, I suggest you use Guava's Files class:

String text = Files.toString("filename.txt", Charsets.UTF_8);

Of course, that's assuming you want to maintain the linebreaks. If you want to remove the linebreaks, you could either load it that way and then use String.replace, or you could use Guava again:

List<String> lines = Files.readLines(new File("filename.txt"), Charsets.UTF_8);
String joined = Joiner.on("").join(lines);

Answer 3

I would strongly advice using library here but since Java 8 you can do this also using streams.

    try (InputStreamReader in = new InputStreamReader(System.in);
         BufferedReader buffer = new BufferedReader(in)) {
        final String fileAsText = buffer.lines().collect(Collectors.joining());
        System.out.println(fileAsText);
    } catch (Exception e) {
        e.printStackTrace();
    }

You can notice also that it is pretty effective as joining is using StringBuilder internally.

Answer 4

If you create a StringBuilder, then you can append every line to it, and return the String using toString() at the end.

You can replace your ReadBigStringIn() with

public String ReadBigStringIn() {
        StringBuilder b = new StringBuilder();

        try {
            String line = buffIn.readLine();
            while (line != null) {
                b.append(line);
                line = buffIn.readLine();
            }
        }
        catch(IOException e){};

        return b.toString();
}

Answer 5

This creates a long string, every line is seprateted from string " " (one space):

public String ReadBigStringIn() {
    StringBuffer line = new StringBuffer();


    try { 
        while(buffIn.ready()) {
        line.append(" " + buffIn.readLine());
    } catch(IOException e){
        e.printStackTrace();
    }

    return line.toString();
}

Answer 6

Sounds like you want Apache IO FileUtils

String text = FileUtils.readStringFromFile(new File(filename + ".txt"));
String[] stringArray = text.split("[^0-9.+Ee-]+");