FileInputStream和FileOutputStream Java

Question

I have a input file that contains on the first line an integer (n) and on the second line n integers.

Example:

7
5 -6 3 4 -2 3 -3

The problem is that my data gets "corrupted". I've been using new File(path) but I'm trying to submit my code to an online compiler to run some tests on it and new File(path) represents a security problem there. Thank you.

public static void main(String[] args) throws IOException {
        FileInputStream fin=new FileInputStream("ssm.in");
        int n;
        n = fin.read();
        a = new int[100];
        for(int i=1;i<=n;i++)
            a[i]=fin.read();
        fin.close();
}

Edit: When I try to print the array a , the result should be:

5 -6 3 4 -2 3 -3

Instead, it is:

13 10 53 32 45 54 32 51 32 52 32 45 50 32 51 32 45 51 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1

Answer 1

Probably your file contains the data as plain text (presumably ASCII), like this:

7
5 -6 3 4 -2 3 -3

If you open the file with FileInputStream and use the read() method to read a single byte from the file, what you actually get is the ASCII character's number. The many -1 which you see are meaning that there's nothing left from the file to be read.

What you actually want to do is convert the ASCII text to a number. For this, you should not read binary data but something that involves char or String , like FileReader and BufferedReader . And you need to involve Integer.parseInt() .

The following listing shows how to read a single number from a text file:

import java.io.*;

public class ReadNumber {
    public static void main(final String... args) throws IOException {
        try (final BufferedReader in = new BufferedReader(new FileReader(args[0]));
            final String line = in.readLine();
            final int number = Integer.parseInt(line);
            System.out.format("Number was: %d%n", number);
        }
    }
}

You can change this source code to your needs accordingly. You might also want to read about the Scanner class and the String.split() method.