java为什么负输入不能在for循环中工作

Question

如果扫描仪输入为负数，则不会显示任何内容。 如果我输入-11，那么10，-10和-1应该是输出

import java.util.Scanner;
public class Factor
{
    public static void main(String[] args)
    {
        Scanner scan = new Scanner(System.in);
        String replay = "replay";
        while(replay.equals("replay"))
        {
        System.out.println("The numbers that add to be ___(number1)___ that multiply to be ___(number2)___ are...");
        System.out.println("Enter number1:");
        int n1 = scan.nextInt();
        System.out.println("Enter number2:");
        int n2 = scan.nextInt();

        System.out.println("Computing...");
        for(double f2 = -1000; f2 <= n1; f2++)
        {
            for(double f1 = -1000; f1 <= n1; f1++)
            {
                if(f1*f2 == n2 && f1+f2 == n1)
                {
                    System.out.println(f1 + " and " + f2);
                }
            }
        }    
        scan.nextLine();
        System.out.println("Enter replay if you would like to compute again");
        replay = scan.nextLine();
        }

    }
}    

即使我的循环变量是负数

Answer 1

你的扫描仪可以读取负数，它工作正常。由于循环结束时n1为-11，因此无法获得预期的输出，因此循环不会到达（f1*f2==n2&；f1+f2==n1）为真的点。如果你迭代，比如从-1000到1000，你会得到想要的输出

此代码：

`import java.util.Scanner;

public class NegativeScanner{
    public static void main(String[] args)
    {
        Scanner scan = new Scanner(System.in);
        String replay = "replay";
        while(replay.equals("replay"))
        {
        System.out.println("The numbers that add to be ___(number1)___ that multiply to be ___(number2)___ are...");
        System.out.println("Enter number1:");
        int n1 = scan.nextInt(); //-11
        System.out.println("Enter number2:");
        int n2 = scan.nextInt(); // 10

        System.out.println("Computing...");
        for(double f2 = -1000; f2 <= 1000; f2++){ //-1000-től -11-ig

            for(double f1 = -1000; f1 <= 1000; f1++){ //-1000-től -11-ig

                if(f1*f2 == n2 && f1+f2 == n1)
                {
                    System.out.println(f1 + " and " + f2);
                }
            }
        }    
        scan.nextLine();
        System.out.println("Enter replay if you would like to compute again");
        replay = scan.nextLine();
        }
    }
}

产生以下输出：

The numbers that add to be ___(number1)___ that multiply to be ___(number2)___ are... Enter number1: -11 Enter number2: 10 Computing... -1.0 and -10.0 -10.0 and -1.0 Enter replay if you would like to compute again