Load and save to txt file

Question

In my previous thread I forgot to show people that I had made an attempt to try this myself, rest assured, i have spent the past 2 hours trying to get this stupid problem solved.

I need to do the following :

• Search for file called "file.txt", if null then create it.
• Read the file to find the integer (should be the only thing in the whole file)
• If the integer doesn't exist then create it and set it to 1
• If it does already exist then add 1 to it, and save it again
• Open the file again, get the integer and print it to the console.

This is as far as I managed to get :

package science;

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.io.Reader;

public class DumpData {

    static void writeStringToFile(String gender, String securityLevel){
        try {




            File file = new File(gender + securityLevel + ".txt");
            //file.getParentFile().mkdirs();

            PrintWriter pr = new PrintWriter(file);

            FileInputStream fs = new FileInputStream(gender + securityLevel + ".txt");
            BufferedReader br = new BufferedReader(new InputStreamReader(fs));
            if (br.readLine() == null) {
                pr.println("" + 0);
            }

            //String first = br.readLine();
            //System.out.println(first);
            try{
                String first = br.readLine();
                  int num = Integer.parseInt(first);
                  int add = (num + 1);
                  pr.println("" + add);
                  pr.close();
                  System.out.println(num);
                } catch (NumberFormatException e) {
                  // not an integer!
                    System.out.println("error");
                    System.out.println(br.readLine());
                }
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    } 
}

I kept getting this the message "error" printed to the console, and with more examination I found that nothing was being saved to the .txt file at all. I fully expected my code to add 1 to the int in the file every time the method was executed.

Answer 1

You're trying to read a line twice

if (br.readLine() == null) {         <-- first time
    pr.println("" + 0);
}

 //String first = br.readLine();
 //System.out.println(first);
 try{
     String first = br.readLine();   <-- second time

The second time will fail because there is no second line.

Instead just do this

String line;
while ((line = br.readLine()) != null){
    int num = Integer.parseInt(line.trim());
    ...
}

You don't need the first if statement

Answer 2

I strongly suggest you to work with Apache COmmons IO when dealing with files.

Here's the link : http://commons.apache.org/proper/commons-io/

Look at the FileUtils class.