如何对包含多行的文件中的一行整数求和 - Java

Question

I am trying to sum numbers in separate lines from a file. In addition, I would like the code to ignore the first number of every line.

3 3 3 3
1 1 1 1 1
2 2  

From these numbers I would like to print out 9, 4 and 2.

Whereas I am getting an answer of 21 as I sum everything apparently with this amateur piece of code:

  while(scan.hasNextInt())  
    {  
        a = a + scan.nextInt();
    } 
    System.out.println(a);

Answer 1

    String input = "3 3 3 3\n1 1 1 1 1\n2 2";
    Scanner scan = new Scanner(input); 
    while(scan.hasNextLine()) {
        Scanner line = new Scanner(scan.nextLine());
        int calculation = 0;
        for(int i = 0;line.hasNextInt();i++) {
            if(i>0) {
                calculation = calculation+line.nextInt();
            }else {
                line.nextInt();
            }
        }
        System.out.println(calculation);
    }

I was able to get your required output using scanners instead of an array to save the lines if the input is from the console or System.in youll have to account for that in the scan variable

Answer 2

Without your other side of codes but I think i understood what you'r trying to do.

So you can take all the line by line and can start from second object.Her is the code:

        String line;
        while((line = scan.nextLine() != null)) {
            String[] lines = line.split(" ");
            int total = 0;
            for(int i = 1; i < lines.length; i++) {
                total += Integer.parseInt(lines[i]);
            }
            
            System.out.println(total);
        }

Answer 3

public static void main(String[] args) throws IOException  {
    List<String> lines = Files.readAllLines(Paths.get("D:\\data.txt"));
    for (String line : lines) {
        String[] numbers = line.split("\\s");
        int result = 0;
        for(int i=1 ; i<numbers.length ; i++) {
            result = result + Integer.parseInt(numbers[i]);
        }
        System.out.println("Line "+line+"  : result "+ result);
    }
}

result

Line 3 3 3 3  : result 9
Line 1 1 1 1 1  : result 4
Line 2 2   : result 2

Answer 4

And for completeness, a stream solution.

try {
    // read in the lines and stream them
    Files.lines(Path.of("f:/source.txt"))

    // split the lines on spaces and stream the tokens
            .map(line -> Arrays.stream(line.split("\\s+"))

    // skip the first one
                    .skip(1)
    // convert each token to an int
                    .mapToInt(Integer::parseInt)
    // sum them
                    .sum())
    // and print each sum
            .forEach(System.out::println);
    // catch and print any exceptions.
} catch (Exception e) {
    e.printStackTrace();
}

Answer 5

Here's a 1-liner:

Files.readAllLines(Paths.get("D:/data.txt")).stream()
.map(line -> line.split(" "))
.map(Arrays::stream)
.mapToInt(stream -> stream.skip(1).mapToInt(Integer::parseInt),sum())
.forEach(System.out::println);