java - 我将如何循环回到开头？

Question

如果数字为负数，我会尝试将其设置为让您重新开始并输入另一个数字的位置。我尝试做一个 while 循环，但它只是放入 System.out.println，我进入了一个无限循环。

    System.out.println("Please input a positive number: ");
    Scanner scan = new Scanner(System.in);
    int num = scan.nextInt();


    if (num < 0) {
        System.out.println("That number is negative.");
    }

    if (num >= 90 && num <= 110) {
        boolean value = true;
    } else if (num >= 190 && num <= 210) {
        boolean value = true;
    }

我以前做过一次这样的事情，我记得一旦我弄明白了它就很简单哈哈。不幸的是，我没有那个文件可以看。有帮助吗？

*编辑开始

   int num = scan.nextInt();
   while (num < 0)
   {
   System.out.println("Please input a positive number: ");
   Scanner scan = new Scanner(System.in);
   }

*编辑 #2

Scanner scan = new Scanner(System.in);
int num = scan.nextInt();
while (num < 0)
{
System.out.println("Please input a positive number: ");
}

*最终工作代码

   int num;
   Scanner scan = new Scanner(System.in);

   while (true)
      {
         System.out.println("Please input a positive number: ");
         num = scan.nextInt();

      if (num < 0)
         { 
            System.out.println("That number is negative.");
         }
      else if ((num >= 90 && num <= 110) || (num >= 190 && num <= 210))
         { 
            System.out.println("true");
            break;
         }
      else
         {
            System.out.println("false");
            break;
         }

      }

Answer 1

如果数字为负数，将再次提示用户，否则跳出循环。

   int num;
   Scanner scan = new Scanner(System.in);

   while (true)
   {
      System.out.println("Please input a positive number: ");
      num = scan.nextInt();

      if (num < 0)
      {
        System.out.println("That number is negative.");
      }
      else if ((num >= 90 && num <= 110) || (num >= 190 && num <= 210))
      {
        break;
      }
   }