java - 打印斐波那契数

Question

我的程序应该根据用户输入的内容输出一个斐波那契数（例如，如果他们输入 7，程序将输出 13）。这部分有效。我遇到问题的部分是程序检查以确保用户输入的数字是正数且小于或等于 70。它应该再次要求用户输入，但它输出“Fibonacci #-1为 0" 并停止。这是我的代码：

import java.util.Scanner;

public class scalvert_Fibonacci
{
public static void main ( String args[] ) 
{
    Scanner input = new Scanner ( System.in );

    int sum = 0;
    int num;
    int f1 = 0, f2 = 0, f3 = 1;

    System.out.print("Which Fibonacci number would you like? ");
    num = input.nextInt(); 

    if (num == 0)
    return 0;

    else if (num == 1)
    return 1;

    while (num < 0 || num > 70)
    {
        System.out.print("Which Fibonacci number would you like? ");
        num = input.nextInt(); 
    }

        for(int i = 1; i <= num; i++)
        {
                f1 = f2;
                f2 = f3;
                f3 = f1 + f2;
        }
        System.out.printf("Fibonacci #%d is %d\n",num, f2);
}
}

Answer 1

我想到了。

while(num < 0 || num > 70)
    {
        System.out.print("Which Fibonacci number would you like? ");
        num = input.nextInt(); 
    }

Answer 2

using this might solve your problem

if(num<0 || num>70)
{
    //ask a number again
}
else
{
    //calculate
}

or use this

if( 0 < num < 71 )
{
    //calculate
}
else
{
     //ask for a valid number
}