Question

在我的代码double getAirSpeed double calcPatternwidth和double calcPatternLength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

Answer 1

您没有正确初始化main中的变量。您显示调用函数并预先分配它们然后显示它们。我认为你所寻找的是main看起来很喜欢这个：

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。我猜这就是你想要完成的事情。

完成后你真的应该关闭扫描仪对象，所以我会在返回之前修改getAirSpeed()来调用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

Answer 2

在这里，我无法看到您在哪里初始化给定的变量。由于所有三个vairables都是main方法的本地，因此编译器不会为它们分配默认值。只是创建那些变量的getter将不会赋值。如果你在类中使用main方法创建变量，编译器将分配defaut值，但你必须使它们为静态，因为main方法是静态的，你不能在静态块中使用非静态变量。

我的变量没有正确初始化

2 个答案: