Question

我是Java的新手，也是while，for和if / else语句的新手。我真的一直在与这个问题的野兽挣扎。

代码和说明如下。它编译，但我没有按预期计算。我不确定这是一个数学逻辑错误，循环布局错误，还是两者兼而有之。

我现在已经磨了很长时间，而且我无法看到它。我觉得我真的很亲密......但还是那么遥远。

代码：

/* 
This program uses a while loop to to request two numbers and output (inclusively) the odd numbers between them, 
the sum of the even numbers between them, the numbers and their squares between 1 & 10, the sum of the squares 
of odd numbers.
*/

import java.io.*;
import java.util.*;

public class SumOfaSquare
{
 static Scanner console = new Scanner(System.in);

 public static void main (String[] args)
 {

 int firstnum = 0, secondnum = 0, tempnum = 0;
 int sum = 0,squaresum = 0, squarenum = 0;
 int number = 1;


 String oddOutputMessage = "The odd numbers between" + firstnum + " and " + secondnum + " inclusively are:";
   String evenSumMessage = "The sum of all even numbers between " + firstnum + " and " + secondnum + "is: ";
   String oddSquareMessage = "The odd numbers and their squares are : ";
   String squareMessage = "The numbers and their squares from 1-10 are : ";

 System.out.println ("Please enter 2 integers. The first number should be greater than the second: ");
 firstnum = console.nextInt();
 secondnum = console.nextInt();

 //used to find out if first number is greater than the second. If not, inform user of error. 
 if (firstnum > secondnum)
 {
  tempnum = firstnum;
  System.out.println ("You entered: " + firstnum + " and: " + secondnum);
 }
 else
  System.out.println ("Your first number was not greater than your second number. Please try again.");

 //while the frist number is greater, do this....
 while (tempnum <= secondnum)
 { 
  //if it's odd....
  if (tempnum %2 == 1)
   {
   oddOutputMessage = (oddOutputMessage + tempnum + " ");
   squaresum = (squaresum + tempnum * tempnum);
   }

  //otherwise it's even.. 
  else
   {
   sum = sum + tempnum;
   evenSumMessage = (evenSumMessage + sum + " ");
   tempnum++;
   }
 }
 // figures squares from 1 - 10
 while (number <=10) 
 {
   squarenum = (squarenum + number * number);
    squareMessage = (squareMessage + number + " " + squarenum);
   number++;
 }



  oddSquareMessage = oddSquareMessage + squaresum;
  System.out.println (oddOutputMessage); 

  System.out.println (oddOutputMessage);
  System.out.println (squareMessage);
  System.out.println (evenSumMessage);
  System.out.println (oddSquareMessage);

 }
}

Answer 1

在第一轮中，请仔细考虑增加tempnum的条件。什么时候发生奇怪的事情？ tempnum会增加吗？

Answer 2

您的代码存在许多问题。我宁愿你自己解决这个问题。如果您不知道如何调试代码，可以使用“println”调试来打印出变量。

输入输入3和1并逐行浏览您的程序，并考虑答案将在您的头脑中（或在纸上）。看看它是否符合您的预期结果。

以下是有关您的代码的一般性评论：

考虑将不同的输出分解为不同的子例程：dumpOddNumbers(low, high), sumEvenNumbers(low, high), ...
尝试尽可能限制变量范围。不要在顶部定义变量，然后再使用它们。尝试在需要之前定义它们。这将限制您的意外后果。除非是临时计数器，否则尽量不要重复使用变量。
while（tempnum＆lt; = secondnum）这些行应该是for个循环。该代码的一个问题是如果第一个数字是＆lt;然后是第二个（例如输入1 10），程序永远循环，因为如果数字是奇数，则tempnum不会递增。
while (tempnum <= secondnum)应该是for (int tempnum = firstnum; tempnum <= secondnum; tempnum++)
while (number <= 10)应为for (int number = 1; number <= 10; number++)
您可以在程序的顶部定义消息，但不应在以后查看结果。做println(msgString + resultValue)。
查看StringBuilder()而不是msg = msg + ...类型的逻辑。效率更高。
当您检查数字的顺序是否正确并吐出错误信息时，您确定要继续吗？我认为你应该return那里。

以下代码与评论不符。哪个是对的？

// while the frist number is greater, do this
while (tempnum <= secondnum) {

希望这有帮助。

循环/数学逻辑时的Java

2 个答案: