Question

我不知道如何初始化半径，以便用户可以在提示时输入半径，而不是将设置值设置为半径。我想我其他所有东西都在这里，但我不能为我的生活弄清楚这一点。我在这里错过了什么？请帮忙

import java.util.Scanner;
import java.text.DecimalFormat;

public class CircleCalc
{
  public static void main(String[]args)
   {
  Scanner keyboard = new Scanner(System.in);
  double radius;
  double area = Math.PI * radius * radius;
  double circum = 2 * radius * Math.PI;
  DecimalFormat formatter = new DecimalFormat("#.0000");
  int choice;


  System.out.println("CIRCLE CALCULATOR MENU");
  System.out.println("1) Calculate the Area of a Circle");
  System.out.println("2) Calculate the CIrcumference of a Circle");
  System.out.println("3) Quit the Program");
  System.out.println("Make a selection by choosing a number:");
  choice = keyboard.nextInt();

  if (choice == 1)
  {
     System.out.println("What is the radius of the Circle?");
     radius = keyboard.nextInt();
     System.out.println(" The Area of the Circle with radius " + radius + " is " + area);
  }

  else if (choice == 2)
  {
     System.out.println("What is the radius of the Circle?");
     radius = keyboard.nextInt();
     System.out.println("The Circumference of the Circle with radius " + radius+ " is " + formatter.format(circum));
  }

  else if (choice == 3)
  {
  System.out.println("You have chosen to quit the program.");
  }

  else if (choice >3)
  {
  System.out.println("You have made an invalid selection.");
  }
   }

}

Answer 1

这是你的问题。

Scanner keyboard = new Scanner(System.in); double radius; double area = Math.PI * radius * radius; double circum = 2 * radius * Math.PI;

您尚未初始化半径值，但同时在计算面积和周长时使用它。首先从用户那里获得输入。先做radius = keyboard.nextInt();。

您可以在获得用户的半径值后进行计算。

希望有所帮助

Answer 2

看起来你想定义函数来计算任何半径的周长和面积（因为你不知道你知道如何计算这些半径的具体半径）< / p>

public static double area(double radius) {
    return Math.PI * radius * radius;
}

public static double circum(double radius) {
    return 2 * radius * Math.PI;
}

然后，当您需要计算结果时，您可以调用这些方法：

System.out.println(" The Area of the Circle with radius " + radius + " is " + area(radius));

和

System.out.println("The Circumference of the Circle with radius " + radius + " is " 
                   + formatter.format(circum(radius)));

如何在此实例中初始化半径？

2 个答案: