如何从Java文件中读取数字？

Question

How can I read inputs (letters, numbers) from my file.txt wherein it reads infinitely but only stops when it encounters special symbols? At the same time when it is numbers ie

123,345,abc

it should translate the ascii code and add the 2 values that results as 123 + 345 = 468

EDITED QUESTION

Here's my code; I really had a problem with reading those bytes in my file.txt. I want to convert its value where Isimilarly added it in my file.txt

public class .... {

    static char tmp = 0;

    public static void main(String[] args) {
        try {
            Reader myReader = new FileReader("MyFolder/myFile2.txt");

            List<Character> myList = new ArrayList<Character>();

            /*for(int myData = myInputStream.read();
                  myData != -1;
                  myData = myInputStream.read()){
                System.out.print(" " + (char)myData);
            }*/

            for(int myData = myReader.read();
                myData != -1;
                myData = myReader.read()){
                if((char)myData != ','){
                    myList.add((char)myData);
                }
                else{
                    continue;
                }
            }
            for(Character i: myList)
            {
                tmp = 1;
            }
            String myString = String.valueOf(tmp);
            int num1 = Integer.parseInt(myString);
            int num2 = Integer.parseInt(myString);
            int equal = num1 + num2;

            System.out.print(equal);

            myReader.close();
        }
        catch(FileNotFoundException e){

        }
        catch(IOException e){

        }
    }
}

Answer 1

Here's some basic code to do what I think you're asking for, building off of what you already have.

public class .... {

    private static final Pattern COMMA = Pattern.compile(",");

    public static void main(String[] args) {
        try {
            BufferedReader myReader =
                    new BufferedReader(new FileReader("MyFolder/myFile2.txt"));

            List<Integer> myList = new ArrayList<Integer>();
            int total = 0;
            String line;
            while ((line = myReader.readLine()) != null) {
                for (String token : COMMA.split(line)) {
                    try {
                        total += Integer.parseInt(token);
                    } catch (NumberFormatException ex) {
                        System.err.println(token + " is not a number");
                    }
                }
            } 

            System.out.print(total);

            myReader.close();
        } catch(FileNotFoundException e){

        } catch(IOException e){

        }
    }
}

Note that it would be better to restructure this so it isn't all in main() , and the exception handling isn't very good, but I'm just going for the basics here.

Answer 2

You're working way too hard, and you're mixing your parsing logic with your file traversal, which is making things seem way more complicated than they actually are:

-traverse the lines of the file;

 BufferedReader r = new BufferedReader(new FileReader(myFile)); 
 String line;
  while ((line=r.readLine())!=null)
 {
   parseLine(line)
  }

-parse the lines of the file into the form you expect. Have it fail if the form is wrong.

private void parseLine(String line)
{
  try{ 
    String[] values = line.split(",");
    //do something useful assuming the line is properly formed
   }
   catch(Exception e)
   {
      //how do you want to handle badly formed lines?
}

Answer 3

You may want to check out the Apache IO project. It greatly simplifies Java file operations.

Once you have this library in place you can use

int finalnumber = 0;
LineIterator it = FileUtils.lineIterator(file, null);
while (it.hasNext()) {
    List<String> segments = Arrays.asList(it.nextLine().split(","));
    for (String segment : segments) {
        try {
            finalnumber += Integer.parseInt(segment);
        } catch (NumberFormatException nfe) {
            //not a number, ignore
        }
    }
}
LineIterator.closeQuietly(it);
System.out.println(finalnumber);

That will add together all numbers on a line of final, ignoring non-numbers.

If someone wants to specify how to do this with the Apache IO, they can post it. I just find the standard Java IO so cumbersome to work with that I avoid it entirely.

Compared to the other code here, this doesn't look much simpler, but Apache IO does do a lot of exception handle and niceties behind the scenes (which you can see since it is open source). If this is all you want to do, your are going to be fine with standard Java IO, but if you wanted to go further with Java IO I still recommended it.