如何从包（java）中的另一个类访问主类中的变量？

Question

我正在做作业，我很难找到问题所在。我写的程序没有编译。请帮忙。作业详情：

“使用以下字段创建一个名为Airport的类：标识符。由纬度和经度组成的坐标（不要分别创建两个！！）。纬度为正表示位于赤道以北，位于南半球则为负。经度为负表示为西，为正表示为格林威治中心以东。一种磁场变化，也表明西部为负，东部为正。没有磁场变化是可以的。海拔高度（英尺）

添加一个静态方法，该方法接受四个双精度，即两个偏移坐标（双lat1、双long1、双lat2、双long2），并使用实验室05中给出的公式返回以海里为单位的距离。例如，圣地亚哥机场的值ID:San，Lat:32.7335556，Long:-117.1896667，Var:14，Elev:16.8'（http://www.airnav.com/airport/SAN）。该类应该为每个字段都有一个访问器和mutator方法。"

我在这里做了大部分工作，但我想我需要在这里添加构造函数。请帮忙

主要类别：

package lab06;

import javax.swing.JOptionPane;

public class Lab06 
{
    public static void main(String[] args) {
        double number;       // To hold the number
        String input;        // To hold user input

        //Create two Airport objects.
        Airport firstAirport = new Airport();
        Airport secondAirport = new Airport();

        // Get and store the coordinates for firstAirport.
        input = JOptionPane.showInputDialog("Enter the first Latitude: ");
        number = Double.parseDouble(input);
        firstAirport.setLatitude(number);
        input = JOptionPane.showInputDialog("Enter the first Longitude: ");
        number = Double.parseDouble(input);
        firstAirport.setLongitude(number);
        input = JOptionPane.showInputDialog("Enter the first Elevation: ");
        number = Double.parseDouble(input);
        firstAirport.setElevation(number);

        // Get and store the coordinates for secondAirport.
        input = JOptionPane.showInputDialog("Enter the second Latitude: ");
        number = Double.parseDouble(input);
        secondAirport.setLatitude(number);
        input = JOptionPane.showInputDialog("Enter the second Longitude: ");
        number = Double.parseDouble(input);
        secondAirport.setLongitude(number);
        input = JOptionPane.showInputDialog("Enter the second Elevation: ");
        number = Double.parseDouble(input);
        secondAirport.setElevation(number);
    }

    // The Distance method calculates the distance in nautical miles
    public static void getDistance(String[] args) 
    {
        double R = 3440;
        double dist = Math.sin(firstAirport.getLatitude())
                * Math.sin(secondAirport.getLatitude())
                + Math.cos(secondAirport.getLatitude())
                * Math.cos(firstAirport.getLatitude())
                * Math.cos(firstAirport.getLongitude()
                        - secondAirport.getLongitude());
        dist = Math.acos(dist);
        dist = dist * R;

        // Display result in nautical miles.
        JOptionPane.showMessageDialog(null,
                "The distance in nautical miles is: %.1f\n" + dist);

        System.exit(0);
    }
}

还有机场舱

package lab06;

public class Airport 
{
    public double latitude;
    public double longitude;
    public double elevation;

    //The setLatitude method stores a value in the latitude field.
    public void setLatitude(double latitude)
    {
        this.latitude = latitude;
    }
    //The setLongitude method stores a value in the longitude field.
    public void setLongitude(double longitude)
    {
        this.longitude = longitude;
    }
    //The setElevation method stores a value in the elevation field.
    public void setElevation (double elevation)
    {
        this.elevation = elevation;
    }
    //The getLatitude method returns an Airport object's latitude.
    public double getLatitude()
    {
        return latitude;
    }
    //The getLongitude method returns an Airport object's longitude.
    public double getLongitude()
    {
        return longitude;
    }
    //The getElevation method returns an Airport object's elevation.
    public double getElevation()
    {
        return elevation;
    }
}

Answer 1

How do I access variables in the main class from another class in the package (java)?

我假定您询问的是访问main中声明的局部变量>&燃气轮机；方法<&书信电报；。简单的答案是你不能

但是您可以将变量的值作为方法或构造函数参数传递给另一个类

I did most of the work here but I think I need to add constructors here.

对。那是个好主意

Please help

提示：阅读您的课堂讲稿/教科书/关于如何编写构造函数的在线Java教程

Answer 2

按照我理解问题的方式，静态方法应该提供数据，而不知道它是在计算机场之间的距离。如果目的是这样做，它将需要接收两个机场对象，而不是所述的4个双倍对象

注意：作为一般规则，避免使任何可变数据静态可用（缓存除外）

Answer 3

下面是一个如何将3个double传递给Airport的示例：

public class Airport {

    public double latitude;
    public double longitude;
    public double elevation;

    public Airport(double latitude, double longitude, double elevation) {

        this.latitude = latitude;
        this.longitude = longitude;
        this.elevation = elevation;

    }

    //if you need to access variables you add get methods like:
    public double getLatitude(){
       return latitude;
    }

    public static void main( String[] args) {

        Airport ap = new Airport(30.34567, 27.6789,  -140); 
        System.out.println("Airport latitude is "+ ap.getLatitude());
    }

}