如果已经有if语句，我怎么能在我的代码中添加一个while循环

Question

已经看过其他帖子，但我不知道何时进入while循环或for循环我的程序运行直到满足条件，输入1到20之间的数字并运行代码。

import java.util.Scanner;

public class MultiplicationTable {

  public static void main(String[] args) {

    Scanner scanner = new Scanner(System.in);
    int number, total;

    System.out.println("Please enter an integer from 1 to 20:");            
    number = scanner.nextInt(); 

        if (number >= 21){  
        System.out.println("Your integer must be between 1 and 20.");
        }
        else if ( number <= 0){
        System.out.println("Your integer must be between 1 and 20.");
        }
        else {    
        for(int i = 1; i<=20; i++){
            total = number * i;
            System.out.println(i + " X " + number + " = " + total);
            }

        }

  }

}

Answer 1

在扫描仪输入周围放置一个循环

while(number < 0 || number > 20)
{
    number = scanner.nextInt();
    // if statements here
}

有了这个，你需要初始化数字，以便进入循环

int number = -1;