读取txt文件。在每一行旁边显示整数之和

Question

45 90 40 30 42 95 64 47 23

14 80 30 84 24 49 16 10 20

我是Java OOP的初学者，这是Txt文件。我必须在每行旁边打印整数的和，然后找出其中最大的和。

我可以读取文件，我试着把每一行都做成一个字符串，但当我把每一行的每一个数字都做成一个整数时，我想不出如何在列结束时停止程序，这样我就可以打印和并转到下一行。

import java.util.Scanner;
import java.io.*;

public class Asst1Problem2{


   public static void main(String[] args){

   int sum = 0;
   int largestSum = 0;

   String line = "";

   try{

      Scanner input = new Scanner(new File("integers2.txt"));


      while(input.hasNextLine()){

         line = input.nextLine();

         System.out.println(line);


      }

   }

   catch(FileNotFoundException fnf){

         System.out.print("no file "  + fnf);

   }

   }
} 

我本想得到总数，但我做得不对。

Answer 1

Scanner input = new Scanner(new File("integers2.txt"));

int maxSum = -1; //Assuming there are no negative values
while(input.hasNextLine()) {
   line = input.nextLine();
   String[] splitted = line.split(" "); //Split the spaces from the line

   int sum = 0;

   for (int i = 0; i < splitted.length; i++) {
       int value = Integer.parseInt(splitted[i]); //Convert the string into an integer
       sum += value;
   }

   System.out.println(sum); //This line sum

   if (sum > maxSum) {
       maxSum = sum;
   }
}

System.out.println(maxSum); //The biggest sum

Answer 2

您好，您可以使用循环或流（java 8）来解决这个问题。我还建议您使用try-with-Resources。

如果没有流，可以使用以下示例

public static void main(String[] args) {
    int largestSum = 0;
    try (Scanner input = new Scanner(new File("integers2.txt"))) {
        while (input.hasNextLine()) {
            String[] numbers = input.nextLine().split(" ");
            int sum = 0;
            for (String s : numbers) {
                if (s.matches("^\\d+$")) { // check if the element was an integer number. 
                    int i = Integer.parseInt(s);
                    sum += i;
                }
            }
            System.out.printf("current sum = %s \\n", sum); // print current sum
            largestSum = Math.max(sum, largestSum);
        }
    } catch (FileNotFoundException fnf) {
        System.out.print("no file " + fnf.getMessage());
    }
    System.out.println(largestSum);
}

有关检查字符串是否为整数的更多详细信息

使用java-8流，以下代码应该可以做到：

public static void main(String[] args) {
    int largestSum = 0;
    try (Scanner input = new Scanner(new File("integers2.txt"))) {
        while (input.hasNextLine()) {
            String[] numbers = input.nextLine().split(" ");
            int sum = Arrays
                            .stream(numbers)
                            .filter(s -> s.matches("^\\d+$"))
                            .mapToInt(s -> Integer.parseInt(s))
                            .sum();
            System.out.printf("current sum = %s \\n", sum); // print current sum
            largestSum = Math.max(sum, largestSum);
        }
    } catch (FileNotFoundException fnf) {
        System.out.print("no file " + fnf.getMessage());
    }
    System.out.println(largestSum);
}