do而循环不会读取循环中输入的变量

Question

对于我的程序，我要编写一个程序，它接受2到10之间的行数。生成n行的乘法三角形。每行包含的条目不超过其行大小。这一点我没有问题。但是，在用户将数字0输入到我的问题“请输入要打印的行数：”之后，应该终止循环并打印“感谢您使用此程序！”我用了一个DO。。。WHILE循环以确定用户是否希望继续。在我的循环中，我将用户想要打印的数字声明为int num。我的循环应该持续到num

import java.io.*;
import java.util.*;
public class Prog166g
{ //begin testshell 
public static void main (String[] args)
{ //begin main
 int i;
    int outer;
    int inner;
    int result;
    int example = 4;
    System.out.print("Number of rows for this triangle : " + example +"\n");
    for ( i = 1; i <= example; i++) {
        System.out.printf("%5s", i);
    }
    System.out.println("");
    for ( outer = 1; outer <= 4; outer++) {
        for ( inner = 1; inner <= outer; inner++) {
            result = outer * inner;
            System.out.printf("%5s", result);
        }
        System.out.println("");
    }
    System.out.println("");

        do{
        System.out.print("Please enter the number of rows you would like to print: ");
        Scanner kbReader = new Scanner(System.in);
        int num = kbReader.nextInt();
        System.out.println("");
        System.out.println("Number of rows for this triangle: " + num);
        for ( i = 1; i <= num; i++) {
            System.out.printf("%5s", i);
        }
        System.out.println("");
        for ( outer = 1; outer <= num; outer++) {
            for ( inner = 1; inner <= outer; inner++) {
                result = outer * inner;
                System.out.printf("%5s", result);
            }
        }
     }while (num>=1);


   System.out.println("Thank you for using this program"); 
}// ends main
}//ends testshell

Answer 1

num变量超出范围。只需在循环上方的某个位置声明它。

int example = 4;
int num; //Declare num here
System.out.print("Number of rows for this triangle : " + example +"\n");
for ( i = 1; i <= example; i++) {
    System.out.printf("%5s", i);
}
System.out.println("");
for ( outer = 1; outer <= 4; outer++) {
    for ( inner = 1; inner <= outer; inner++) {
        result = outer * inner;
        System.out.printf("%5s", result);
    }
    System.out.println("");
}
System.out.println("");

    do{
    System.out.print("Please enter the number of rows you would like to print: ");
    Scanner kbReader = new Scanner(System.in);
    num = kbReader.nextInt();
    System.out.println("");
    System.out.println("Number of rows for this triangle: " + num);
    for ( i = 1; i <= num; i++) {
        System.out.printf("%5s", i);
    }
    System.out.println("");
    for ( outer = 1; outer <= num; outer++) {
        for ( inner = 1; inner <= outer; inner++) {
            result = outer * inner;
            System.out.printf("%5s", result);
        }
    }
 }while (num>=1);


  System.out.println("Thank you for using this program"); 
}// ends main
}//ends testshell

Answer 2

您的“num”声明必须在“do”之前。这可以是：

...
int num;
do {
    ...
    num = kbReader.nextInt();
    ...;
}
...