Read line with Scanner

Question

EDIT for further readers: the problem was that my input file was corrupted.

I don't understand what I'm doing wrong :

I was using this code :

    File f = new File("C:\\Temp\\dico.txt");
    BufferedReader r = null;
    try {
        r = new BufferedReader(new FileReader(f));
        String scan;
        while((scan=r.readLine())!=null) {
            if(scan.length()==0) {continue;}
            //treatment
        }
    } catch (FileNotFoundException ex) {
        Logger.getLogger(Lexique.class.getName()).log(Level.SEVERE, null, ex);
    } catch (IOException ex) {
        Logger.getLogger(Lexique.class.getName()).log(Level.SEVERE, null, ex);
    } finally {
        if(r!=null) try {
            r.close();
        } catch (IOException ex) {
            Logger.getLogger(Lexique.class.getName()).log(Level.SEVERE, null, ex);
        }
    }

Which is working fine. Now, for some reason, I wanted to change for a Scanner. My code became :

    File f = new File("C:\\Temp\\dico.txt");
    Scanner r = null;
    try {
        r = new Scanner(f);
        String scan;
        while(r.hasNextLine()) {
            scan = r.nextLine();
            if(scan.length()==0) {continue;}
            //treatment
        }
    } catch (FileNotFoundException ex) {
        Logger.getLogger(Lexique.class.getName()).log(Level.SEVERE, null, ex);
    } catch (IOException ex) {
        Logger.getLogger(Lexique.class.getName()).log(Level.SEVERE, null, ex);
    } finally {
        if(r!=null) r.close();
    }

This time, we never enter the while, because r.hasNextLine() always returns "false". Any idea about what I'm doing wrong ?

I precise that nothing else changed, the file is still the same.

EDIT : I also precise that I tried with another file and got the same result, meaning it doesn't comes from the file apparently.

The file looks like this :

a
à
abaissa
abaissable
abaissables
abaissai
abaissaient
abaissais
abaissait
...

Edit 2 : The content of the file seems to be problematic since the problem persists only if I copy/paste the content from my file to another. In clear, if I write the content myself, it works, if I use a part of the content of my dico.txt file, it doesn't work. Any explanation ?

Edit 3 : These are the links to my files. I advice you to avoid the dico.txt which is very huge.

dico.txt : https://drive.google.com/file/d/0B0sroFy9HZlBNDl3MUwzVnh6VU0/edit?usp=sharing

test.txt : https://drive.google.com/file/d/0B0sroFy9HZlBemZjbXU1RmlmdjQ/edit?usp=sharing

Answer 1

This code reads the file line by line.

public static void readFileByLine(String fileName) {
  try {
   File file = new File(fileName);
   Scanner scanner = new Scanner(file);
   while (scanner.hasNext()) {
    System.out.println(scanner.next());
   }
   scanner.close();
  } catch (FileNotFoundException e) {
   e.printStackTrace();
  } 
 }

You can also set a delimiter as a line separator and then perform the same.

 scanner.useDelimiter(System.getProperty("line.separator"));

You have to check whether there is a next token available and then read the next token. You will also need to doublecheck the input given to the Scanner. i.e. dico.txt. By default, Scanner breaks its input based on whitespace. Please ensure that the input has the delimiters in right place

UPDATED ANSWER for your comment:

I just tried to create an input file with the content as below

a
à
abaissa
abaissable
abaissables
abaissai
abaissaient
abaissais
abaissait

tried to read it with the below code.it just worked fine.

 File file = new File("/home/keerthivasan/Desktop/input.txt");
     Scanner scr = null;
         try {
            scr = new Scanner(file);
            while(scr.hasNext()){
                System.out.println("line : "+scr.next());
            }
        } catch (FileNotFoundException ex) {
            Logger.getLogger(ScannerTest.class.getName()).log(Level.SEVERE, null, ex);
        }

Output:

line : a
line : à
line : abaissa
line : abaissable
line : abaissables
line : abaissai
line : abaissaient
line : abaissais
line : abaissait

so, I am sure that this should work. Since you work in Windows ennvironment, The End of Line (EOL) sequence (0x0D 0x0A, \r\n) is actually two ASCII characters, a combination of the CR and LF characters. if you set your Scanner instance to use delimiter as follows, it will pick up probably

 scr = new Scanner(file);
 scr.useDelimiter("\r\n");

and then do your looping to read lines. Hope this helps!

Answer 2

next() and nextLine() methods are associated with Scanner and is used for getting String inputs. Their differences are...

next() can read the input only till the space. It can't read two words separated by space. Also, next() places the cursor in the same line after reading the input.

nextLine() reads input including space between the words (that is, it reads till the end of line \n). Once the input is read, nextLine() positions the cursor in the next line.

Read article :Difference between next() and nextLine()

Replace your while loop with :

while(r.hasNext()) {
                scan = r.next();
                System.out.println(scan);
                if(scan.length()==0) {continue;}
                //treatment
            }

Using hasNext() and next() methods will resolve the issue.

Answer 3

/*
 * To change this license header, choose License Headers in Project Properties.
 * To change this template file, choose Tools | Templates
 * and open the template in the editor.
 */
package javaapplication1;

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

/**
 *
 * @author zsagga
 */
class openFile {
        private Scanner x ; 
        int count = 0 ; 
        String path = "C:\\Users\\zsagga\\Documents\\NetBeansProjects\\JavaApplication1\\src\\javaapplication1\\Readthis.txt"; 


    public void openFile() {
//                System.out.println("I'm Here");
        try {
            x = new Scanner(new File(path)); 

        } 
        catch (Exception e) {
            System.out.println("Could not find a file");
        }
    }

    public void readFile() {

        while (x.hasNextLine()){
            count ++ ;
            x.nextLine();     
        }
        System.out.println(count);
    }

    public void closeFile() {
        x.close();
    }
}

/*
 * To change this license header, choose License Headers in Project Properties.
 * To change this template file, choose Tools | Templates
 * and open the template in the editor.
 */
package javaapplication1;

/**
 *
 * @author zsagga
 */
public class JavaApplication1 {

    public static void main(String[] args) {
        // TODO code application logic here
        openFile r =  new openFile(); 
        r.openFile(); 
        r.readFile();
        r.closeFile(); 

    }
}

Answer 4

---

For everybody who still can't read in a simple .txt file with the Java scanner.

---

I had the problem that the scanner couldn't read in the next line, when I Copy and Pasted the information, or when there was to much text in my file.

The solution is: Coder your .txt file into UTF-8.
This can be done fairly simple by saving opening the file again and changing the coding to UTF-8. (Under Win7 near the bottom right corner)

The Scanner shouldn't have any problem after this.

Answer 5

Try to use r.hasNext() instead of r.hasNextLine():

while(r.hasNext()) {
        scan = r.next();