java - 我的变量未正确初始化

在我的double getAirSpeed double calcPatternwidth和double calcPatternLength下面的代码中，未正确初始化，为什么？

/**
 * holding patterns
 * assignment 1
 * question 2
 **/

import java.util.Scanner;

public class StockiColeA1Q2  {

  public static void main(String []args)  {
    Scanner keyboard = new Scanner(System.in);

    double getAirSpeed ;
    double calcPatternWidth;
    double calcPatternLength;

    System.out.println("That speed is " + getAirSpeed +
                       "\nHolding pattern width: " + calcPatternWidth +
                       "kms\nHolding pattern length: " + calcPatternLength + "kms");

  }//main

  public static double getAirSpeed() {
    Scanner keyboard = new Scanner(System.in);

    System.out.println("Enter the speed in Knots: ");
      double knots = keyboard.nextDouble(); //knots given by user

      return knots*1.852;

  }//get air speed

  public static double calcPatternWidth(double knots) {

  return (knots/60*Math.PI)*2;

  }//patern width

  public static double calcPatternLength(double knots) {

    return knots/60 + (knots/60*Math.PI)*2;


  }//pattern width

}//class

最佳答案

您没有正确初始化main中的变量。您可以显示调用函数并在前面分配它们，然后显示它们。我认为您正在寻找的是一个看起来像这样的main：

public static void main(String[] args) {
    double getAirSpeed = getAirSpeed();
    double calcPatternWidth = calcPatternWidth(getAirSpeed);
    double calcPatternLength = calcPatternLength(getAirSpeed);

    System.out.println("That speed is " + getAirSpeed + "\nHolding pattern width: " + calcPatternWidth
            + "kms\nHolding pattern length: " + calcPatternLength + "kms");

}// main

上面的代码使用getAirSpeed作为calcPatternWidth和calcPatternLength的参数。我想这就是您想要实现的目标。

完成后，您实际上应该关闭Scanner对象，以便在返回之前将getAirSpeed()修改为调用keyboard.close()。

public static double getAirSpeed() {
    Scanner keyboard = new Scanner(System.in);

    System.out.println("Enter the speed in Knots: ");
    double knots = keyboard.nextDouble(); // knots given by user

    keyboard.close();
    return knots * 1.852;

}// get air speed