需要帮助Java简单规则形状面积计算器和if语句吗

Question

我试图完成一个java项目，制作一个程序，该程序需要输入3&；之间的规则形状；6边然后计算边的长度并打印。这是我第一次使用java，所以我有点不确定从第25行开始出现的错误，我觉得“'x'不能解析为变量”。我认为我做的数学是正确的，所以这可能是一个简单的解决办法，但我已经尝试了一段时间，并求助于要求澄清。任务的唯一规定是需要一个if语句来运行代码，实现给定边数的适当公式，并将结果存储在变量中

以下是迄今为止的完整代码：

import java.util.Scanner;

public class RegularShapeArea {

    public static void main(String[] args) {
    
    //user input takes number of sides between 3 & 6 and stores in 'sides'
        
    System.out.println("How many sides does the shape have (between 3 and 6)? ");
    Scanner sidenum = new Scanner(System.in);
    double sides = sidenum.nextDouble();
    
    //if statement to determine user input is between 3 & 6 or presents and error message
    
    if((sides <3) || (sides >6)) { 
        System.out.println("The value entered was not between 3 & 6.");
    }
    //else statement runs user input for length of sides if it is within correct parameters and storees value in 'lengths'
    else {
        System.out.println("How long is each side? ");
        Scanner sidelength = new Scanner(System.in);
        double length = sidelength.nextDouble();
    }

    if (length == 3) {
        double calculation = (Math.sqrt(3)/4) * (length *length);
    }
    else if (length == 4) {
        calculation = (length * length);
    }
    else if (length == 5) {
        calculation = (Math.sqrt(5 * (5 + 2 * (Math.sqrt(5)))) * length * length) / 4;
    }
    else if (length == 6){
        calculation = ((3 * Math.sqrt(3) * (length * length)) / 2);
    }
    
    
    System.out.Println("The surface are of a shape with" + sides + "sides, each of length" + sidelength + "is " + calculation);
    }

}

在此方面的任何帮助都将不胜感激

Answer 1

我认为因为double calculation是在if语句中声明的，所以不能在else if中使用它，因为它只存在于第一个if语句中。在if和else if之前声明它，以便能够在所有语句中使用它