CODEWITHSUNDEEP
javanullpointerexception
Tacolips
Tacolips

Reputation: 11

NullPointerException - reading not empty file returns Null

I'm fairly new to programming and I wanted to learn how to read data from a file. I watched this video and tried to copy the idea for my own purpose. https://www.youtube.com/watch?v=3RNYUKxAgmw

Whenever I try to run my main it says Error Line 22 - NullPointerException. I have a text file with numbers and I have checked if the names match. I simply do not understand why it says my file is empty. 

package uge4;
import java.util.*;
import java.io.*;

public class ReadFile {

    private Scanner x;
    public void openFile () {
        try {
            x = new Scanner (new File("gradeconverter.txt"));
        } catch(FileNotFoundException e){
            System.out.println("File not found.");
        }
    }

    public void readFile() {
        Scanner input = new Scanner(System.in);
        System.out.print("Insert old grade ");
        int grade = input.nextInt();
        input.close();

    // line 22 
    while(x.hasNextInt()) {
        int a = x.nextInt();
        int b = x.nextInt();
        if ( a == grade) {
            System.out.println("Your new grade is: "+b);
        }
    }
}

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

Upvotes: 0

Views: 201

Answers (3)

Manu Zi
Manu Zi

Reputation: 2370

Can u simply use the java 8 "way"

Files.lines(Paths.get(FILE_PATH)).forEach(System.out::print);

PS: You have forget to open the Scanner -> x

Upvotes: 0

TheNorthon
TheNorthon

Reputation: 121

After first int a = x.nextInt() calls another int b = x.nextInt();, it may happend that x Scanner has no more data to return. You need to check x.hasNextInt() before each call of x.nextInt() method.

Upvotes: 2

Parth Anjaria
Parth Anjaria

Reputation: 3971

i guess it is because you havnt specified the path of your file

if you are uding a file from your pc/latop's harddisk please give the complete path

x = new Scanner (new File("C://newfolder//gradeconverter.txt"));// just an example, add the actual path of you files location

Upvotes: 0

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