39

I use InputStream to read some data, so I want to read characters until new line or '\n'.

Ahmad Naoum
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    Use a `BufferedReader` and its `readLine` method. Dupe of: http://www.stackoverflow.com/questions/5868369/how-to-read-a-large-text-file-line-by-line-using-java – Tunaki Jan 22 '16 at 19:41

3 Answers3

103

You should use BufferedReader with FileInputStreamReader if your read from a file

BufferedReader reader = new BufferedReader(new FileInputStreamReader(pathToFile));

or with InputStreamReader if you read from any other InputStream

BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream));

Then use its readLine() method in a loop 

while(reader.ready()) {
     String line = reader.readLine();
}

But if you really love InputStream then you can use a loop like this 

InputStream stream; 
char c; 
String s = ""; 
do {
   c = stream.read(); 
   if (c == '\n')
      break; 
   s += c + "";
} while (c != -1);
Datz
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Tommaso Pasini
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  • I was hoping for something bulid-in :/. Btw. BufferedReader doesn't support encoding. – Radim Nyč Nov 22 '17 at 15:00
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    What do you mean by built in? BufferedReader is in the java standard library and it actually does, you can specify the encoding in this way: ``new BufferedReader(new InputStreamReader(new FileInputStream("path/to/file"), "UTF8"));`` – Tommaso Pasini Nov 23 '17 at 15:08
  • Didn't know that. I found that you can do this with InputStream and then I wanted to find out if there is any way how to make InputStream readLines without a while cycle. I will try mentioned BufferedReader constructor... – Radim Nyč Dec 03 '17 at 18:59
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    well for anyone who stumbles on this in the future like me, it's FileReader not FileInputStreamReader – Krusty the Clown Dec 23 '21 at 19:52
  • reader.ready() does not always return true, leading to no lines read. More failure proven: String line = null; while ((line = reader.readLine()) != null) { ... } – kaiser Oct 18 '22 at 14:29
10

TL;DR

Use BufferedReader within the try-with block, which will close the resource after finishing with it.

It is possible to read the input stream with BufferedReader and with Scanner. If you don't have a good reason, it is better to use BufferedRead (for broad discussion BufferedReader vs Scanner see).

I would also suggest using the Buffered Reader with try-with-resources to make sure the resource are auto-closed. see

See the following code

try (BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream))) {
        while (reader.ready()) {
            String line = reader.readLine();
            System.out.println(line);
        }
    }catch (FileNotFoundException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
Memin
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5

For files, the following will let you read each line:

import java.io.FileNotFoundException;
import java.util.Scanner;
import java.io.File;

public static void readText throws FileNotFoundException(){

     Scanner scan = new Scanner(new File("filename.txt"));

     while(scan.hasNextLine()){
         String line = scan.nextLine();

     }
}
Rana
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