read digits (instead of int) from a txt file in java

Question

I have a file like this

test.txt:

122352352246

12413514316134

Now I want to read each digit a time, and store it as one element in, say, a list. I tried using Scanner. But it will read a line each time, and outputs a long integer. That means if I want to get the digits, I need to further separate the digits in that integer. I guess there must be an elegant way to directly read one digit each time. Below is my code

public class readDigits {

public static void main(String[] args) throws IOException{
    List<Integer> list = new ArrayList<Integer>();
    File file = new File("test.txt");
    Scanner in = new Scanner(file);
    int c;
    try {
         while (in.hasNext()){
             c = in.nextInt();
             list.add(c);

        }

    }
    finally {
        System.out.println(list);
        in.close();
    }

}


}

possible dup: http://stackoverflow.com/questions/811851/how-do-i-read-input-character-by-character-in-java — santosh-patil, Dec 10 '14 at 17:10
This looks like it may help you. http://stackoverflow.com/questions/13942701/take-a-char-input-from-the-scanner — jcd, Dec 10 '14 at 17:13
@zhang_rick You can use method charAt() to read one letter/digit at a time — foxt7ot, Dec 10 '14 at 17:16

Jon Skeet · Answer 1 · 2014-12-10T17:54:36.183

I guess there must be an elegant way to directly read one digit each time.

A digit is a character - so you want to read a single character at a time.

Oddly enough, Scanner doesn't appear to be conducive to that. You could read a byte at a time from Scanner, but it would possibly be better to use a Reader instead:

List<Integer> list = new ArrayList<Integer>();
try (Reader reader = Files.newBufferedReader(Paths.get("test.txt"))) {
    int c;
    while ((c = reader.read()) != -1) {
        char ch = (char) c;
        int value = Character.getNumericValue(ch);
        if (value >= 0) {
            list.add(value);
        }
    }
}
System.out.println(list);

Alternatively, you could read all the lines of the file, and process each line individually - that would be pretty simple too.

score 0 · Answer 2 · answered Dec 10 '14 at 17:13

0

Try this:

byte[] buffer = new byte[2];
try (InputStream str = new FileInputStream("test.txt")) {
    while (str.read(buffer) != -1) {
        System.out.print(new String(buffer));
    }
}

answered Dec 10 '14 at 17:13

Halmackenreuter

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read digits (instead of int) from a txt file in java

2 Answers2