Java在循环中使用if语句

Question

我写了一个小代码：

System.out.println("Please enter a number");
int number = scan.nextInt();

if(number == 1) {
    System.out.println("Number is 1");
} else if(number == 2) {
    System.out.println("Number is 2");
} else {
    System.out.println("Invalid selection");
}

当用户输入不同于1和2的数字时，用户会收到“无效选择”消息，然后代码终止。我不希望它终止，我希望它再次运行，直到用户写入1或2。我试着做while循环，但它变成了一个无限循环。你有什么建议

Answer 1

您可以在这里使用while循环

 Scanner scanner = new Scanner(System.in);
 boolean status = true;
 while (status) { // this runs if status is true
    System.out.println("Please enter a number");
     int number = scanner.nextInt();
     if (number == 1) {
        System.out.println("Number is 1");
        status=false; // when your condition match stop the loop
     } else if (number == 2) {
        System.out.println("Number is 2");
        status=false;// when your condition match stop the loop
     } else{
        System.out.println("Invalid selection");
     }
 }

Answer 2

@Dosher，重新发布@Raj_89的答案，并在while循环条件下进行更正。请注意，同时循环条件

int number = 0;
        do{
            System.out.println("Please enter a number");
            Scanner scan = new Scanner(System.in);
            number = scan.nextInt();
          if(number == 1)
            {
              System.out.println("Number is 1") ;
            }

          else if(number == 2)
           {
              System.out.println("Number is 2") ;
            }
          else
           {
              System.out.println("Invalid selection") ;
            }
         }while(number==1 || number==2);

Answer 3

试试这个

int number;
do{
    System.out.println("Please enter a number");
    number = scan.nextInt();
  if(number == 1)
    {
      System.out.println("Number is 1") ;
    }

  else if(number == 2)
   {
      System.out.println("Number is 2") ;
    }
  else
   {
      System.out.println("Invalid selection") ;
    }
 }while(number!=1 && number!=2);

Answer 4

我建议您在调用^{}之前，先检查是否存在带有^{}的int。如果您在while循环中使用它，那么这将是一个很好的循环测试条件

Scanner scan = new Scanner(System.in);
System.out.println("Please enter a number");
while (scan.hasNextInt()) {
    int number = scan.nextInt();
    if (number == 1) {
        System.out.println("Number is 1");
        break;
    } else if (number == 2) {
        System.out.println("Number is 2");
        break;
    } else {
        System.out.println("Invalid selection");
    }
}
// ...