Java.util.Scanner 转 int

Question

如何将“dryrun.txt”中存储的数字设置为 int url？我知道这是一个非常简单的答案，但我似乎无法理解。我看过其他关于使用 parseInt 的帖子，但是当我这样做时，我总是收到错误，我问了我的老师，他说这仅用于在其他文本中查找数字，在这个文件中它只有 1 个数字。感谢您的帮助。

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

public class Even
{
  public static void main (String[] args) throws IOException
  {
    int even = 0;
    int url = 0;
    int Counter = 2;
    Scanner fileScan;

    fileScan = new Scanner (new File("dryrun.txt"));
    url = fileScan.nextInt();

    if ( url > 2)
      System.out.println ("Error");      
    if (url % 2 == 0)
      even = (Counter + 2);

    System.out.print(" "+ even +" "); 
  }
}

Answer 1

Okay, yeah you're right sorry I didn't realize that but anyway I still have my original problem, the value in the file is 0 now and it gives me the Error but if I set it to 2 it adds four and doesn't give me the error..

这表明你的逻辑是错误的......

根据此代码，让我们进行一些桌面检查...

if ( url > 2)
  System.out.println ("Error");      
if (url % 2 == 0)
  even = (Counter + 2);

假设url == 4 ...

• if (url > 2) =if (4 > 2) =true ，打印Error
• if (url % 2 == 0) =if (4 % 2 == 0) =true , even = Counter + 2

假设url == 2 ...

• if (url > 2) =if (2 > 2) =false ，什么都不做...
• if (url % 2 == 0) =if (2 % 2 == 0) =true , even = Counter + 2

假设你想在数字超过1时打印错误你应该使用if (url >= 2)或if (url > 1)

假设出现错误时您不想继续计算结果，则应该使用 if-else声明，大致如下...

if ( url > 2)
  System.out.println ("Error");      
else if (url % 2 == 0) {
  even = (Counter + 2);
  System.out.print(" " + even + " ");
}