Java Reading integers from a file into an array

Question

File fil   new File  Tall txt    FileReader inputFil   new FileReader fil   BufferedReader in   new BufferedReader inputFil    int    tall   new int  100    String s  in readLine     while s  null        int i   0      tall i    Integer parseInt s     this is line 19     System out println tall i        s   in readLine       in close      I am trying to use the file  Tall txt  to write the integers contained in them into the array named  tall   It does this to some extent  but also when I run it  it throws the following exception     Exception in thread  main  java lang NumberFormatException  For input string         at java lang NumberFormatException forInputString Unknown Source      at java lang Integer parseInt Unknown Source      at java lang Integer parseInt Unknown Source      at BinarySok main BinarySok java 19    Why exactly does it do this  and how do I remove it  As I see it  I read the file as strings  and then convert it to ints  which isn t illegal

User · Answer

It looks like Java is trying to convert an empty string into a number. Do you have an empty line at the end of the series of numbers?

You could probably fix the code like this

String s = in.readLine();
int i = 0;

while (s != null) {
    // Skip empty lines.
    s = s.trim();
    if (s.length() == 0) {
        continue;
    }

    tall[i] = Integer.parseInt(s); // This is line 19.
    System.out.println(tall[i]);
    s = in.readLine();
    i++;
}

in.close();

User · Answer

You must have an empty line in your file   You may want to wrap your parseInt calls in a  try  block   try     tall i      Integer parseInt s     catch  NumberFormatException ex      continue      Or simply check for empty strings before parsing   if  s length      0     continue    Note that by initializing your index variable i inside the loop  it is always 0  You should move the declaration before the while loop   Or make it part of a for loop

User · Answer

For comparison  here is another way to read the file  It has one advantage that you don t need to know how many integers there are in the file   File file   new File  Tall txt    byte   bytes   new byte  int  file length     FileInputStream fis   new FileInputStream file   fis read bytes   fis close    String   valueStr   new String bytes  trim   split    s     int   tall   new int valueStr length   for  int i   0  i  lt  valueStr length  i         tall i    Integer parseInt valueStr i    System out println Arrays asList tall

User · Answer

You might want to do something like this  if you re in java 5  amp  up   Scanner scanner   new Scanner new File  tall txt     int    tall   new int  100   int i   0  while scanner hasNextInt        tall i      scanner nextInt

User · Answer

You might want to do something like this  if you re in java 5  amp  up   Scanner scanner   new Scanner new File  tall txt     int    tall   new int  100   int i   0  while scanner hasNextInt        tall i      scanner nextInt

User · Answer

It looks like Java is trying to convert an empty string into a number. Do you have an empty line at the end of the series of numbers?

You could probably fix the code like this

String s = in.readLine();
int i = 0;

while (s != null) {
    // Skip empty lines.
    s = s.trim();
    if (s.length() == 0) {
        continue;
    }

    tall[i] = Integer.parseInt(s); // This is line 19.
    System.out.println(tall[i]);
    s = in.readLine();
    i++;
}

in.close();

User · Answer

For comparison  here is another way to read the file  It has one advantage that you don t need to know how many integers there are in the file   File file   new File  Tall txt    byte   bytes   new byte  int  file length     FileInputStream fis   new FileInputStream file   fis read bytes   fis close    String   valueStr   new String bytes  trim   split    s     int   tall   new int valueStr length   for  int i   0  i  lt  valueStr length  i         tall i    Integer parseInt valueStr i    System out println Arrays asList tall

User · Answer

You might have confusions between the different line endings   A Windows file will end each line with a carriage return and a line feed   Some programs on Unix will read that file as if it had an extra blank line between each line  because it will see the carriage return as an end of line  and then see the line feed as another end of line

User · Answer

You might have confusions between the different line endings   A Windows file will end each line with a carriage return and a line feed   Some programs on Unix will read that file as if it had an extra blank line between each line  because it will see the carriage return as an end of line  and then see the line feed as another end of line

User · Answer

File file   new File  E  Responsibility txt          Scanner scanner   new Scanner file       List lt Integer gt  integers   new ArrayList lt  gt         while  scanner hasNext              if  scanner hasNextInt                  integers add scanner nextInt               else               scanner next                        System out println integers

User · Answer

You must have an empty line in your file   You may want to wrap your parseInt calls in a  try  block   try     tall i      Integer parseInt s     catch  NumberFormatException ex      continue      Or simply check for empty strings before parsing   if  s length      0     continue    Note that by initializing your index variable i inside the loop  it is always 0  You should move the declaration before the while loop   Or make it part of a for loop

User · Answer

File file   new File  E  Responsibility txt          Scanner scanner   new Scanner file       List lt Integer gt  integers   new ArrayList lt  gt         while  scanner hasNext              if  scanner hasNextInt                  integers add scanner nextInt               else               scanner next                        System out println integers

User · Answer

It looks like Java is trying to convert an empty string into a number. Do you have an empty line at the end of the series of numbers?

You could probably fix the code like this

String s = in.readLine();
int i = 0;

while (s != null) {
    // Skip empty lines.
    s = s.trim();
    if (s.length() == 0) {
        continue;
    }

    tall[i] = Integer.parseInt(s); // This is line 19.
    System.out.println(tall[i]);
    s = in.readLine();
    i++;
}

in.close();

User · Answer

You might have confusions between the different line endings   A Windows file will end each line with a carriage return and a line feed   Some programs on Unix will read that file as if it had an extra blank line between each line  because it will see the carriage return as an end of line  and then see the line feed as another end of line

User · Answer

You might have confusions between the different line endings   A Windows file will end each line with a carriage return and a line feed   Some programs on Unix will read that file as if it had an extra blank line between each line  because it will see the carriage return as an end of line  and then see the line feed as another end of line

User · Answer

You might want to do something like this  if you re in java 5  amp  up   Scanner scanner   new Scanner new File  tall txt     int    tall   new int  100   int i   0  while scanner hasNextInt        tall i      scanner nextInt

User · Answer

You must have an empty line in your file   You may want to wrap your parseInt calls in a  try  block   try     tall i      Integer parseInt s     catch  NumberFormatException ex      continue      Or simply check for empty strings before parsing   if  s length      0     continue    Note that by initializing your index variable i inside the loop  it is always 0  You should move the declaration before the while loop   Or make it part of a for loop

User · Answer

You must have an empty line in your file   You may want to wrap your parseInt calls in a  try  block   try     tall i      Integer parseInt s     catch  NumberFormatException ex      continue      Or simply check for empty strings before parsing   if  s length      0     continue    Note that by initializing your index variable i inside the loop  it is always 0  You should move the declaration before the while loop   Or make it part of a for loop

User · Answer

You might want to do something like this  if you re in java 5  amp  up   Scanner scanner   new Scanner new File  tall txt     int    tall   new int  100   int i   0  while scanner hasNextInt        tall i      scanner nextInt

User · Answer

It looks like Java is trying to convert an empty string into a number. Do you have an empty line at the end of the series of numbers?

You could probably fix the code like this

String s = in.readLine();
int i = 0;

while (s != null) {
    // Skip empty lines.
    s = s.trim();
    if (s.length() == 0) {
        continue;
    }

    tall[i] = Integer.parseInt(s); // This is line 19.
    System.out.println(tall[i]);
    s = in.readLine();
    i++;
}

in.close();

[java] Java: Reading integers from a file into an array

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