java - 扫描仪提示用户输入数字

Question

以下是我尝试遵循的说明:

Write a method called negative sum that accepts a scanner reading input from a file containing a series of integers., and a print message to the console indicating whether the sum starting from the first number is ever negative.You should alse return true if a negative sum can be reached and false if not. for example, suppose the file contains the 38 4 19 -27 -15 -3 4 19 38 your method would consider the sum of just number (38) , the first two numbers ( 38 + 4) the firs three number ( 38 + 4 + 19) and so on to the asnd . none of thes sume is negative so the method would produce the following output and return false : No negative numbers.

If the file instead contains 14 7 -10 9 -18 -10 17 42 98 the method finds that a negative sum of -8 is reached after adding the first six numbers. it should output the following to the console and return true: sum of -8 after 6 steps.

这就是我到目前为止所拥有的。我只是在添加扫描仪以提示用户输入数字时遇到问题。

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

public class NegativeSum{
    public static void main (String [] args )
    throws FileNotFoundException{


        negativesum();


        }//end of amin

public static boolean negativesum()
throws FileNotFoundException{


     File file = new File ("negativeSum.txt");
    Scanner input =  new Scanner (file);

    int sum=0;
    int count = 0;

    while ( input.hasNextInt()){
        int next =input.nextInt();
        sum+=next;
        count++;

        if ( sum<0){
            System.out.println("sum of " + sum + " after " + count + "steps" );
            return true;
            }

        }///end of while
    System.out.println("no negative sum ");
    return false;




    }//end of metho d

}//end of main

Answer 1

我在您的实现中看到的唯一严重错误(相对于您的问题陈述)是您的方法应该接收 Scanner 作为输入(例如接受扫描仪) -

public static boolean negativeSum(Scanner input) {
  if (input == null) {
    // Handle null - e.g. no value
    return false;
  }
  int sum = 0;
  int count = 0;

  while (input.hasNextInt()) {
    int next = input.nextInt();
    sum += next;
    count++;

    if (sum < 0) {
      System.out.println("sum of " + sum + " after "
          + count + " steps");
      return true;
    }
  }// /end of while
  System.out.println("no negative sum");
  return false;
}