CODEWITHSUNDEEP
javafile-ionewlinefileinputstream
JavaNewbie_M107
JavaNewbie_M107

Reputation: 2037

File input using FileInputStream does not work properly

The following program should print the String "Humpty Dumpty sat on a wall,\n Humpty Dumpty had a great fall." to a file and input it back. 

package io;

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.PrintStream;

public class ByteIO {

    /**
     * @param args
     */
    public static void main(String[] args) {
        String output = "Humpty Dumpty sat on a wall,\n Humpty Dumpty had a great fall.";
        System.out.println("Output String : " + output);
        try(PrintStream out = new PrintStream("F:\\Test.txt")) {
            out.println(output);
        } catch(FileNotFoundException e) {
            e.printStackTrace();
        }

        String input = "";
        try(FileInputStream in = new FileInputStream("F:\\Test.txt")) {
            while(in.read() != -1)
                input += (char)in.read();
        } catch(FileNotFoundException e) {
            e.printStackTrace();
        } catch(IOException e) {
            e.printStackTrace();
        }
        System.out.println("Input String : " + input);
    }
}

However, the String I got from the FileInputStream was "upyDmt a nawl, upyDmt a ra al?"! Also, when I opened the file "Test.txt" I found that the output String had become "Humpty Dumpty sat on a wall, Humpty Dumpty had a great fall." in a single line. Where did the \n go?

Upvotes: 0

Views: 1526

Answers (4)

Hunter McMillen
Hunter McMillen

Reputation: 61550

You are calling in.read() twice:

while(in.read() != -1)
    input += (char)in.read();

This reads two characters each iteration instead of one, so you are effectively discarding a character each time.

Try storing the character in the while condition, then just adding that character to input:

EDIT: based on JavaNewbie_M107's comment

int i;    
while((i = in.read()) != -1)
   input += (char)i;

Upvotes: 4

JavaNewbie_M107
JavaNewbie_M107

Reputation: 2037

This is the correct solution to my problem : 

int i = 0;
char c;
    do {
        c = (char)i;
        input += c;
        i = in.read();
    } while(i != -1);

The extra space at the front is removed by using a .trim() method.

Upvotes: 0

Ravi
Ravi

Reputation: 31437

As Hunter said, you need to change your code to this 

char c;
while((c=in.read()) != -1)
input += c;

Upvotes: 0

SJuan76
SJuan76

Reputation: 24895

For the second part, Windows (and many applications like Notepad) do not recognize \n as new line. In Windows, \r\n marks a new line. Try opening with a more serious edit program (WordPad should suffice) and you will see it correctly formatted.

Upvotes: 1

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