Java - Only read first line of a file

Question

I only want to read the first line of a text file and put that first line in a string array.

This is what I have but its reading the whole file.

ex text in myTextFile:

Header1,Header2,Header3,Header4,Header5
1,2,3,4,5
6,7,8,9,10





String line= System.getProperty("line.separator");
String strArray[] = new String[5];


String text = null;
BufferedReader brTest = new BufferedReader(new FileReader(myTextFile));
    text = brTest .readLine();
        while (text != line) {
            System.out.println("text = " + text );
             strArray= text.split(",");
         }

Also, [here's how you compare strings in java](http://stackoverflow.com/questions/513832/how-do-i-compare-strings-in-java). — Sotirios Delimanolis, Jul 10 '14 at 03:03
If you only want to read the first line, why do you have a loop? — Hot Licks, Jul 10 '14 at 03:05

score 23 · Answer 1 · answered Jul 10 '14 at 03:06

23

use BufferedReader.readLine() to get the first line.

BufferedReader brTest = new BufferedReader(new FileReader(myTextFile));
    text = brTest .readLine();
   System.out.println("Firstline is : " + text);

answered Jul 10 '14 at 03:06

bumbumpaw

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2

And add brTest.close() or better use the try (BufferedReader...) { } construction of Java 8. – Anthony Jun 25 '16 at 10:21
@Anthony, `try (..)` is Java 7 syntax :) – Adir Dayan Oct 12 '21 at 19:22

score 17 · Accepted Answer · answered Jul 10 '14 at 03:02

17

If I understand you, then

String text = brTest.readLine();
// Stop. text is the first line.
System.out.println(text);
String[] strArray = text.split(",");
System.out.println(Arrays.toString(strArray));

answered Jul 10 '14 at 03:02

Elliott Frisch

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score 8 · Answer 3 · edited May 23 '17 at 11:47

8

With Java 8 and java.nio you can also do the following:

String myTextFile = "path/to/your/file.txt";
Path myPath = Paths.get(myTextFile);
String[] strArray = Files.lines(myPath)
    .map(s -> s.split(","))
    .findFirst()
    .get();

If TAsks assumption is correct, you can realize that with an additional

.filter(s -> !s.equals(""))

edited May 23 '17 at 11:47

Community

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1

answered Jan 18 '16 at 16:44

feob

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Be careful: Files.lines does not auto close the file. – FRotthowe Sep 11 '18 at 11:41
3

will it actually load all content to memory? – Yeung Mar 02 '22 at 10:21
2

@Yeung, yes, It will load the full file as stream. From the docs: "Read all lines from a file as a Stream. Bytes from the file are decoded into characters using the UTF-8 charset." If your will work with medium-large files better use bufferedReader solution – JuniorGuy Jul 11 '22 at 09:13

tmucha · Answer 4 · 2018-08-07T10:07:32.680

4

Also, beside of all other solutions presented here, you could use guava utility class (Files), like below:

import com.google.common.io.Files;
//...

String firstLine = Files.asCharSource(myTextFile).readFirstLine();

edited Aug 07 '18 at 10:07

answered Sep 15 '17 at 12:39

tmucha

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Do you have a link to where the guave utility can be found and how it can be imported? – Paul Velthuis Aug 07 '18 at 08:56
1

Added in answer. – tmucha Aug 07 '18 at 10:07

akash · Answer 5 · 2014-07-10T06:25:06.253

1

I think you are trying to get one line only if it's not empty.

You can use

 while ((text=brTest .readLine())!=null){
    if(!text.equals("")){//Ommit Empty lines
         System.out.println("text = " + text );
         strArray= text.split(",");
         System.out.println(Arrays.toString(strArray));
         break;
    }
 }

edited Jul 10 '14 at 06:25

answered Jul 10 '14 at 03:06

akash

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score 1 · Answer 6 · edited Dec 04 '18 at 16:40

I hope this will help someone

to read the first line:

public static String getFirstLine() throws IOException {
    BufferedReader br = new BufferedReader(new FileReader("C:\\testing.txt")); 

    String line = br.readLine(); 
    br.close();
    return line;
}

to read the whole text:

public static String getText() throws IOException {
    BufferedReader br = new BufferedReader(new FileReader("C:\\testing.txt")); 
    StringBuilder sb = new StringBuilder(); 
    String line = br.readLine(); 

    while (line != null) { 
        sb.append(line).append("\n"); 
        line = br.readLine(); 
    } 
    String fileAsString = sb.toString();
    br.close();
    return fileAsString;
}

score 0 · Answer 7 · answered Jul 10 '14 at 06:31

Use this

BuffereedReader reader = new BufferedReader(new FileReader(textFile));
StringBuilder builder = new StringBuilder();

StringBuilder sb = new StringBuilder();
String line = br.readLine();

        while (line != null) {
            sb.append(line);
         break;
        }
if(sb.toString.trim().length!=0)
System.out.println("first line"+sb.toString);

Jack · Answer 8 · 2014-07-10T03:23:50.823

-1

You need to change the condition of your loop

  String[] nextLine;   
  while((nextLine = brTest.readLine()) != null) {
      ...
  }

ReadLine reads each line from beginning up to the occurrence of \r andor \n You can also use tokenizer to split the string

String[] test = "this is a test".split("\\s");

In addition it seems the file is of type CSV if it is please mention that in the question.

edited Jul 10 '14 at 03:23

answered Jul 10 '14 at 03:08

Jack

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@Unihedron I changed the syntax – Jack Jul 10 '14 at 03:12
This is a correct, idiomatic approach to read a file, especially when filtering into a `StringBuilder`. Unfortunately it appears not to answer the question. – Unihedron Jul 10 '14 at 03:14
@Unihedron whats wrong with it ? it reads all lines one by one, questioner can break the loop after reading the first line. – Jack Jul 10 '14 at 03:17
Actually, __[empty lines are returned `""` through `.readLine()`](http://docs.oracle.com/javase/7/docs/api/java/io/BufferedReader.html#readLine())__. Only when the reader has reached end of stream, will `.readLine() != null` return false. Maybe you want `!= null && ! .equals("")`? – Unihedron Jul 10 '14 at 03:18
readline stop reading the line as soon as it reaches to a \n or \r, once it reaches to those put whatever it read into nextLine then you can use the nextLine string which contains a line of the file. – Jack Jul 10 '14 at 03:22
Empty lines in text files are essentially multiple `\n\r`s. – Unihedron Jul 10 '14 at 03:23
is it a CSV file ? is this your question? – Jack Jul 10 '14 at 03:24

Java - Only read first line of a file

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