java - 我尝试运行这段代码，它运行时不会抛出错误，问题是它不会执行 for 循环我只是一个初学者，所以请

Question

求 2 和输入值之间所有偶数的和？

import java.util.Scanner;

public static void main(String[] args) {
    //initialization and declaration of variable
    int input, sum = 0;
    Scanner sc = new Scanner(System.in);

    //Ask user to input data
    System.out.print("Enter a number you want to limit up-to : ");
    input = sc.nextInt();

    //Conditions
    if(input < 2) {
        System.out.println("Error Occurred! Please, Enter a number greater or equal to 2. ");
    }

    for (int i = 2; i <= input; i++ ) {
        if( i % 2 == 0) {
            sum += i;
        }
    }
}

Answer 1

您应该打印结果sum。在 main 方法关闭之前添加 System.out.println("the sum is:"+ sum) 。完整代码如下:

import java.util.Scanner;
public class Test {
        public static void main(String[] args) {
        //initialization and declaration of variable
        int input, sum = 0;
        Scanner sc = new Scanner(System.in);

        //Ask user to input data
        System.out.print("Enter a number you want to limit up-to : ");
        input = sc.nextInt();

        //Conditions
        if(input < 2) {
            System.out.println("Error Occurred! Please, Enter a number greater or equal to 2. ");
        }

        for (int i = 2; i <= input; i++) {
            if( i % 2 == 0) {
                sum += i;
            }
        }
        System.out.println("the sum is:" + sum);
    }
}

作为Tim-Hunter也就是说，你可以将i的步长设置为2。因为如果i是偶数，则i+1一定是奇数。代码如下:

for (int i = 2; i <= input; i+=2) {
  if( i % 2 == 0) {
    sum += i;
  }
}