否则没有如果 [英] Else without if

问题描述

我正在尝试为周一到期的项目编写计算机编程课程的代码，而且我对 Java 还很陌生，但我正在尝试编写一个程序，该程序将首先确定用户输入的数字是偶数还是奇数，然后确定该数字是否为素数.我不确定我的算法是否正确，所以如果有人对我的算法或其他任何程序有任何更正，请说出来，但我真正的问题是该程序拒绝编译.每次我尝试时，它都说它有一个 else 没有问题.这是我的命令框的链接:

I'm trying to write a code for my computer programming class for a project due Monday, and I'm pretty new to Java, but I'm trying to write a program that will first determine if a number the user inputs is even or odd and then determine if the number is prime or not. I'm not sure if I did the algorithm right or not, so if anyone has any corrections on the program to my algorithm or anything else please say so, but my real issue is that the program is refusing to compile. Every time I try, it says it's having an else without if problem. Here's a link to my command box:

http://s1341.photobucket.com/user/Emi_Nightshade/media/Capture_zps45f9a2ea.png.html

这是我的代码:

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

public class Lesson9p1_ThuotteEmily
{
    public static void main(String args[])
    {
        Scanner kbReader0=new Scanner(System.in);
        System.out.print("

Please enter an integer. An integer is whole number, and it can be either negative or positive. Please enter your number: ");
        long num=kbReader0.nextLong();

        if(num%2==0)                                     //if and else with braces
        {
           System.out.println("Your integer " + num + " is even.");
        }
        else
        {
            System.out.println("Your integer " + num + " is odd.");
        }

        Scanner kbReader1=new Scanner(System.in);
        System.out.print("

Would you like to know if your number is prime? Please enter yes or no: ");
        String yn=kbReader1.nextLine();

        if(yn.equals.IgnoreCase("Yes"))
        {
            System.out.println("Okay. Give me a moment.");

            {
                if(num%2==0)
                {
                    System.out.println("Your number isn't prime.");
                }
                else if(num==2)
                {
                    System.out.println("Your number is 2, which is the only even prime number in existence. Cool, right?");
                }
                for(int i=3;i*i<=n;i+=2)
                {
                    if(n%1==0)
                    {
                        System.out.println("Your number isn't prime.");
                    }
                }
                else
                {
                    System.out.println("Your number is prime!");
                }
            }
        }
        if(yn.equals.IgnoreCase("No"))
        {
            System.out.println("Okay.");
        }
    }
}

如果有人能帮我解决这个问题，以及我在程序其他地方可能遇到的任何问题，我将不胜感激！谢谢.

If anyone could help me out with this and also any problems I may have made elsewhere in the program, I'd be very grateful! Thanks.

推荐答案

在 for 循环后有一个 else 语句

you have an else statement after a for loop

for(int i=3;i*i<=n;i+=2)
{
    if(n%1==0)
    {
        System.out.println("Your number isn't prime.");
    }
}
else
{
    System.out.println("Your number is prime!");
}

您可能必须创建一个布尔变量才能执行此操作.有多种方法可以做到这一点，但我可能会使用这里的一种

you probably have to make a Boolean variable to do this one. there are various ways to do it, but here's one that I would probably use

boolean isPrime = true;
for(int i=3;i*i<=n;i+=2)
{
    if(n%1==0)
    {
        isPrime = false;
    }
}
if(isPrime)
{
    System.out.println("Your number is prime!");
}
else
{
    System.out.println("Your number isn't prime.");
}

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